Hardened Optical Windows with Anti-Reflective Films Having Low Visible Reflectance and Transmission for Infrared Sensing Systems

This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 63/414,128 filed on Oct. 7, 2022, and U.S. Provisional Application Ser. No. 63/525,029 filed on Jul. 5, 2023, the contents of which are relied upon and incorporated herein by reference in their entirety.

The present disclosure relates to protective covers for sensor systems. Particularly, the present disclosure relates to protective covers including layered films so that the protective cover exhibits antireflective properties over a 50 nm wavelength of interest from 850 nm to 850 nm while exhibiting a dark, opaque appearance.

Light detection and ranging (“LIDAR”) systems include an electromagnetic radiation emitter and a sensor. The electromagnetic radiation emitter emits an electromagnetic radiation emitter beam, which may reflect off an object, and the sensor detects the reflected electromagnetic radiation emitter beam. The electromagnetic radiation emitter beams can be continuous wave, pulsed, frequency modulated, or otherwise distributed across a radial range to detect objects across a field of view. Information about the object can be deciphered from the properties of the detected reflected electromagnetic radiation emitter beam. Distance of the object from the electromagnetic radiation emitter beam can be determined from the time of flight from emission of the electromagnetic radiation emitter beam to detection of the reflected electromagnetic radiation emitter beam. If the object is moving, path and velocity of the object can be determined from shifts in radial position of the emitted electromagnetic radiation emitter beam being reflected and detected as a function of time, as well as from Doppler frequency measurements in some cases.

LIDAR systems in automobiles, and other infrared sensing systems in exposed environments, such as aerospace or home security applications, need to be protected from the environment and various sources of damage, for example, with a covering lens or cover glass window. Vehicles are another potential application for LIDAR systems, with the LIDAR systems providing spatial mapping capability to enable assisted, semi-autonomous, or fully autonomous driving. In such applications, the electromagnetic radiation emitter and sensor are mounted on the roof of the vehicle or on a low forward portion of the vehicle. Electromagnetic radiation emitters emitting electromagnetic radiation having a wavelength outside the range of visible light, such as at 905 nm or 1550 nm are considered for vehicle LIDAR applications. To protect the electromagnetic radiation emitter and sensor from impact from rocks and other objects, a window is placed between the electromagnetic radiation emitter and sensor, and the external environment in the line of sight of the electromagnetic radiation emitter and sensor. A window is similarly placed between the electromagnetic radiation emitter/sensor and the external environment for other applications of the LIDAR system, such as aerospace and home security applications. However, there is a problem in that rocks and other objects impacting the window scratch and cause other types of damage to the window, which cause the window to scatter the emitted and reflected electromagnetic radiation emitter beams, thus impairing the effectiveness of the LIDAR system.

The present disclosure solves that problem with a window that includes first and second layered films. The first layered film may face away from an electromagnetic radiation emitter/sensor when installed in a LIDAR system and include a scratch resistant layer embedded therein to provide damage resistance to the window. Thus, rocks and other objects impacting the window are less likely to cause defects to the window that scatter the emitted and reflected electromagnetic radiation from the LIDAR sensor, resulting in improved performance. In addition, the first and second layered films further include alternating layers of materials having different indices of refraction (including the material providing the hardness and scratch resistance), such that the number of alternating layers and their thicknesses can be configured so that the window has high transmissivity and low reflection in a desired wavelength range (e.g., over a 50 nm wavelength range about a center wavelength between 850 nm and 950 nm). The alternating layers of material may be further selected such that the window transmits and reflects relatively low amounts of radiation in the visible spectrum, thereby providing the window with aesthetically pleasing dark appearance while diminishing signal noise caused by visible light that may otherwise impinge on a detector of a LIDAR system.

An aspect (1) of the present disclosure pertains to a window for a sensing system comprising: a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate; a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film; a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film; and a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa, wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average percentage transmittance, calculated over a 50 nm wavelength range of interest centered at a wavelength between 850 nm and 950 nm, of greater than 90% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°; an average reflectance, calculated over the 50 nm wavelength range of interest between 850 nm and 950 nm, of less than 4% for light incident on the first surface and the second surface at angles of less than or equal to 15°; and an average percentage transmission, calculated from 400 nm to 700 nm, of less than 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

An aspect (2) of the present disclosure pertains to a window according to the aspect (1), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over the 50 nm wavelength range of interest, of greater than 85% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

An aspect (3) of the present disclosure pertains to a window according to the aspect (2), wherein the average P polarization transmittance and the average S polarization transmittance, calculated over the 50 nm wavelength range of interest, are greater than 89% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

An aspect (4) of the present disclosure pertains to a window according to any of the aspects (1)-(3), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has a CIELAB L* value for reflection of less than or equal to 37 for angles of incidence of less than or equal to 60° on the first layered film.

An aspect (5) of the present disclosure pertains to a window according to the aspect (4), wherein the CIELAB L* value for reflection is less than or equal to 25 for angles of incidence of less than or equal to 50° on the first layered film.

An aspect (6) of the present disclosure pertains to a window according to any of the aspects (1)-(5), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has CIELAB a* and b* values for reflection of greater than or equal to −6.0 and less than or equal to 6.0 when viewed from a side of the first layered film.

An aspect (7) of the present disclosure pertains to a window according to any of the aspects (1)-(6), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over the 50 nm wavelength range of interest, of greater than 95% for light normally incident on the first surface and the second surface.

An aspect (8) of the present disclosure pertains to a window according to any of the aspects (1)-(7), wherein: the refractive index of the substrate for electromagnetic radiation having a wavelength of 905 nm is from about 1.45 to about 1.55, the substrate is a glass substrate or a glass-ceramic substrate, the refractive index of the one or more higher refractive index materials is from about 1.7 to about 4.0, and wherein the refractive index of the one or more lower refractive index materials is from about 1.3 to about 1.6, and a difference in the refractive index of any of the one or more higher refractive index materials and any of the one or more lower refractive index materials is about 0.5 or greater.

An aspect (9) of the present disclosure pertains to a window according to any of the aspects (1)-(8), wherein: one of the alternating layers of the first layered film that is farthest from the substrate forms a terminal surface material of the window, the terminal surface material of the window comprising the lower refractive index material, and the first layered firm comprises a scratch resistant layer formed of one of the one or more higher refractive index materials and having a thickness of greater than or equal to 1500 nm and less than or equal to 5000 nm.

An aspect (10) of the present disclosure pertains to a window according to the aspect (9), wherein the scratch resistant layer is separated from the terminal surface by a plurality of the alternating layers of the one or more lower index materials and the one or more higher index materials of the first layered film.

An aspect (11) of the present disclosure pertains to a window according to the aspect (10), wherein the scratch resistant layer is separated from the terminal surface by at least 1000 nm.

An aspect (12) of the present disclosure pertains to a window according to the aspect (1)-(11), wherein the one or more higher refractive index materials of the second layered film comprise silicon having an extinction coefficient of less than or equal to 0.01 over the 50 nm wavelength range of interest.

An aspect (13) of the present disclosure pertains to a window according to the aspect (12), wherein the extinction coefficient is less than or equal to 0.005 over the 50 nm wavelength range of interest.

An aspect (14) of the present disclosure pertains to a window according to the aspect (13), wherein the second layered film comprises two or more silicon layers.

An aspect (15) of the present disclosure pertains to a window according to the aspect (14), wherein a silicon layer of the second layered film most proximate to the substrate comprises the smallest thickness of the two or more silicon layers.

An aspect (16) of the present disclosure pertains to a window according to the aspect (15), wherein a combined thickness of the silicon layers contained in the second layered film is greater than or equal to 500 nm.

An aspect (17) of the present disclosure pertains to a window according to any of the aspects (12)-(16), wherein a layer of the one or more higher refractive index materials in the second layered film is not silicon.

An aspect (18) of the present disclosure pertains to a window according to any of the aspects (1)-(17), wherein the maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, is at least 15 GPa.

An aspect (19) of the present disclosure pertains to a window according to any of the aspects (1)-(18), wherein a hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, is at least 14 GPa over a depth range of 400 nm to 1000 nm.

An aspect (20) of the present disclosure pertains to a window for a sensing system comprising: a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate; a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film; a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film; and a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa, wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average reflectance, calculated over a 50 nm wavelength range of interest centered at a wavelength between 850 nm and 950 nm, of less than 4% for light incident on the first surface and the second surface at angles of less than or equal to 15°; a CIELAB L* value for reflection of less than or equal to 37 for angles of incidence of less than or equal to 60° on the first layered film; and CIELAB a* and b* values for reflection of greater than or equal to −6.0 and less than or equal to 6.0 when viewed from a side of the first layered film.

An aspect (21) of the present disclosure pertains to a window according to the aspect (20), wherein the CIELAB L* value for reflection is less than or equal to 25 for angles of incidence of less than or equal to 50° on the first layered film.

An aspect (22) of the present disclosure pertains to a window according to any of the aspects (20)-(21), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over the 50 nm wavelength range of interest, of greater than 95% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

An aspect (23) of the present disclosure pertains to a window according to any of the aspects (20)-(22), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 400 nm to 700 nm, of less than 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

An aspect (24) of the present disclosure pertains to a window according to any of the aspects (20)-(23), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over the 50 nm wavelength range, of greater than 85% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

An aspect (25) of the present disclosure pertains to a window according to the aspect (24), wherein the average P polarization transmittance and the average S polarization transmittance, calculated over the 50 nm wavelength range of interest, are greater than 89% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

An aspect (26) of the present disclosure pertains to a window according to any of the aspects (20)-(25), wherein the maximum hardness, measured at the layered film and by the Berkovich Indenter Hardness Test, is at least 15 GPa.

An aspect (27) of the present disclosure pertains to a window according to any of the aspects (20)-(26), wherein: one of the alternating layers of the first layered film that is farthest from the substrate forms a terminal surface material of the window, the terminal surface material of the window comprising the lower refractive index material, the first layered firm comprises a scratch resistant layer formed of one of the one or more higher refractive index materials and having a thickness that is greater than or equal to 1500 nm and less than or equal to 5000 nm.

An aspect (28) of the present disclosure pertains to a window according to the aspect (27), wherein: the scratch resistant layer is separated from the terminal surface by a plurality of the alternating layers of the one or more lower index materials and the one or more higher index materials of the first layered film, and the scratch resistant layer is separated from the terminal surface by at least 1000 nm.

An aspect (29) of the present disclosure pertains to a window according to any of the aspects (20)-(28), wherein the one or more higher refractive index materials of the second layered film comprise silicon having an extinction coefficient of less than or equal to 0.004 over the 50 nm wavelength range of interest.

An aspect (30) of the present disclosure pertains to a window according to the aspect (29), wherein the second layered film comprises two or more silicon layers.

An aspect (31) of the present disclosure pertains to a window according to the aspect (30), wherein a silicon layer of the second layered film most proximate to the substrate comprises the smallest thickness of the two or more silicon layers.

An aspect (32) of the present disclosure pertains to a window according to the aspect (31), wherein a combined thickness of the silicon layers contained in the second layered film is greater than or equal to 500 nm.

An aspect (33) of the present disclosure pertains to a window according to any of the aspects (29)-(32), wherein a layer of the one or more higher refractive index materials in the second layered film is not silicon.

An aspect (34) of the present disclosure pertains to a window for a sensing system comprising: a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate; a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film; a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film, wherein the one or more higher refractive index materials of the second layered film comprises silicon; and a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 15 GPa, wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average reflectance, calculated over a 50 nm wavelength range of interest centered at a wavelength between 850 nm and 950 nm, of less than 4% for light incident on the first surface and the second surface at angles of less than or equal to 15°; and an average percentage transmittance, calculated over the 50 nm wavelength range of interest, of greater than 95% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

An aspect (35) of the present disclosure pertains to a window according to the aspect (34), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 400 nm to 700 nm, of less than 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

An aspect (36) of the present disclosure pertains to a window according to any of the aspects (34)-(35), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 850 nm and 950 nm, of greater than 85% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

An aspect (37) of the present disclosure pertains to a window according to the aspect (36), wherein the average P polarization transmittance and the average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 850 nm and 950 nm, are greater than 89% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

An aspect (38) of the present disclosure pertains to a window according to any of the aspects (34)-(37), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has a CIELAB L* value for reflection of less than or equal to 37 for angles of incidence of less than or equal to 60° on the first layered film.

An aspect (39) of the present disclosure pertains to a window according to the aspect (38), wherein the CIELAB L* value for reflection is less than or equal to 25 for angles of incidence of less than or equal to 50° on the first layered film.

An aspect (40) of the present disclosure pertains to a window according to any of the aspects (34)-(39), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has CIELAB a* and b* values for reflection of greater than or equal to −6 and less than or equal to 6 when viewed from a side of the first layered film.

An aspect (41) of the present disclosure pertains to a window according to any of the aspects (34)-(40), wherein: one of the alternating layers of the first layered film that is farthest from the substrate forms a terminal surface material of the window, the terminal surface material of the window comprising the lower refractive index material, the first layered firm comprises a scratch resistant layer formed of one of the one or more higher refractive index materials and having a thickness that is greater than or equal to 1500 nm and less than or equal to 5000 nm.

An aspect (42) of the present disclosure pertains to a window according to the aspect (41), wherein: the scratch resistant layer is separated from the terminal surface by a plurality of the alternating layers of the one or more lower index materials and the one or more higher index materials of the first layered film, and the scratch resistant layer is separated from the terminal surface by at least 1000 nm.

An aspect (43) of the present disclosure pertains to a window according to any of the aspects (34)-(42), wherein the second layered film comprises two or more silicon layers having an extinction coefficient of less than or equal to 0.01 over the 50 nm wavelength range of interest.

An aspect (44) of the present disclosure pertains to a window according to the aspect (43), wherein a silicon layer of the second layered film most proximate to the substrate comprises the smallest thickness of the two or more silicon layers.

An aspect (45) of the present disclosure pertains to a window according to the aspect (44), wherein a combined thickness of the silicon layers contained in the second layered film is greater than or equal to 500 nm.

An aspect (46) of the present disclosure pertains to a window according to any of the aspects (43)-(45), wherein a layer of the one or more higher refractive index materials in the second layered film is not silicon.

An aspect (47) of the present disclosure pertains to a window according to the aspect (46), wherein the layer of the one or more higher refractive index materials in the second layered film that is not silicon is the layer of the one or more higher refractive index materials that is most proximate to the substrate.

An aspect (48) of the present disclosure pertains to a window according to any of the aspects (34)-(47), further comprising a perfluoropolyether layer disposed on the first layered film.

An aspect (49) of the present disclosure pertains toa window according to either of the aspect (14) or the aspect (30), wherein the second layered film comprises a layer of TCO material, wherein the two or more silicon layers are disposed between the layer of TCO material and the substrate.

An aspect (50) of the present disclosure pertains to a window according to the aspect (49), wherein the layer of TCO material comprises a sheet resistance that is greater than or equal to 140Ω/□ and less than or equal to 210Ω/□, wherein the layer of TCO material comprises a thickness that is greater than or equal to 20 nm and less than or equal to 30 mm.

An aspect (51) of the present disclosure pertains to a window according to the aspect (50), wherein the layer of TCO material is indium tin oxide and comprises an extinction coefficient that is less than or equal to 0.05 throughout the 50 nm wavelength range of interest.

An aspect (52) of the present disclosure pertains to a window according to any of the preceding aspects, wherein an inner AR stack separates two or more silicon layers from an inner terminal surface of the second layered film, wherein the inner AR stack comprises at least two layers of the one or more higher refractive index materials that are not silicon.

An aspect (53) of the present disclosure pertains to a window according to the aspect (52), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance, calculated over the 50 nm wavelength range of interest, of less than 0.5% for light incident on the inner terminal surface at angles of incidence of less than or equal to 15°.

An aspect (54) of the present disclosure pertains to a window according to any of the aspects (51)-(53), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated from 400 nm to 700 nm, of less than 1% for light normally incident on the first surface and the second surface °.

An aspect (55) of the present disclosure pertains to a window according to any of the aspects (51)-(54), wherein: the second layered film comprises at least ten silicon layers, and the inner AR stack comprises less than two layers of the one or more higher refractive index materials that are not silicon.

An aspect (56) of the present disclosure pertains to a window according to the aspect (55), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window exhibits a polarization averaged reflectance range (max-min) that is less than 0.5% for light that is incident on the first layered film at a 15° angle of incidence, calculated over the wavelength range from 850 nm to 950 nm.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments.

Reference will now be made in detail to embodiments of windows for use in LIDAR sensors. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The windows comprise described herein may include first and second layered films that are constructed of alternating layers of higher and lower refractive index materials and configured to provide relatively high transmittance and low reflectance in a desired infrared wavelength range of interest. When the window is installed in a LIDAR system, the first layered film may face away from the sensor/electromagnetic radiation emitter and be exposed to an external environment, while the second layered film may face the sensor/electromagnetic radiation emitter. That is, when the LIDAR system is viewed from the outside, an observer may view the first layered film. Light emitted by the electromagnetic radiation emitter may be initially incident on the second layered film prior to propagating through the substrate. In accordance with the present disclosure, the first layered films of the windows described herein may include one or more scratch resistant layers that are relatively thick (e.g., greater than or equal to 500 nm) of a high refractive index material. The scratch resistant layer may be embedded within the first layered film such that the window comprises a maximum nanoindentation hardness of greater than or equal to 8 GPa (e.g., greater than or equal to 10 GPa, greater than or equal to 12 GPa, greater than or equal to 14 GPa) when measured at the first layered film by the Berkovich Indenter Hardness Test. Such nanoindentation hardness can be at a depth of 1 μm within the first layered film. Such nanoindentation hardness beneficially provides scratch resistance and improves performance of the LIDAR system.

In aspects, the alternating layers of the first and second layered films of the windows described herein are also constructed to provide optical performance attributes that are desirable for operation of the LIDAR system in the infrared spectrum. In embodiments, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over at least a 50 nm, 60 nm, 70 nm, 80 nm, or 90 nm wavelength range of interest centered about a wavelength in a range from 850 nm to 950 nm, of greater than 90% (e.g., greater than or equal to 95%) for light incident on the first surface and the second surface at angles of incidence of 15° or less. In embodiments, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has a transmittance of greater than or equal to 92%, and preferably greater than or equal to 94%, and even more preferably greater than or equal to 96% throughout the spectral range from 950 nm to 950 nm for light at normal incidence. The quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films may be configured so that the window also comprises an average percentage P-polarization transmittance and S-Polarization transmittance, calculated over the 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest, of greater than 85% (e.g., greater than or equal to 89%, greater than or equal to 90%, greater than or equal to 93%) for light incident on the first surface and the second surface at an angle of incidence of 60 degrees or less. In embodiments, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance, calculated over the 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest, of less than or equal to 5.0% (e.g., less than or equal to 4.0%, less than or equal to 3.0%, less than or equal to 2.0%, less than or equal to 1.0%) for light incident on the first surface and the second surface at angles of incidence of 15° or less. In aspects, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance (for both S and P-polarizations), off of the second layered film of less than 4.0% (e.g., less than or equal to 3.0%, less than or equal to 2.0%, less than or equal to 1.0) at angles of incidence of less than 15°. In aspects, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance (for both S and P-polarizations), off of the second layered film of less than 5.5% (e.g., less than or equal to 5.0%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.0%, less than or equal to 1.0) at angles of incidence of less than 45°. In aspects, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance (for both S and P-polarizations), off of the second layered film of less than 8.0% (e.g., less than or equal to 7.5%, less than or equal to 7.0%, less than or equal to 6.5%, less than or equal to 6.0%, less than or equal to 5.0%, less than or equal to 5.0%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.0%, less than or equal to 1.0) at angles of incidence of less than 60°.

In further aspects, the first and second layered films of the windows described herein may also be structured to have relatively low reflectance and transmittance of visible light, thereby providing the window with an aesthetically pleasing dark appearance and eliminating signal noise. In embodiments, for example, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 400 nm to 700 nm of less than 5% (e.g., less than or equal to 4.5%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%) for light incident on the first layered film at angles of incidence of 15° or less. In embodiments, for example, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 450 nm to 650 mm nm of less than 1% for light normally incident on the first layered film. Such low transmission of visible light may be achieved by incorporating absorber layers into the second layered film in the amounts described herein.

The windows can also exhibit low reflection in the visible wavelength range. In embodiments, for example, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance, calculated from 450 nm to 650 nm of less than 10% (e.g., less than or equal to 9.0%, less than or equal to 8.0%, less than or equal to 7.0%, less than or equal to 6.0%, less than or equal to 5.0%, less than or equal to 4.5%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%) for light incident on the first layered film at angles of incidence of 15° or less ∘. In embodiments, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance, calculated from 450 nm to 650 nm of less than 12% (e.g., less than or equal to 11%, less than or equal to 10%, less than or equal to 9.0%, less than or equal to 8.0%, less than or equal to 7.0%, less than or equal to 6.0%, less than or equal to 5.0%, less than or equal to 4.5%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%) for light incident on the first layered film at angles of incidence of 45° or less ∘. In embodiments, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage reflectance, calculated from 450 nm to 650 nm of less than 16% (e.g., less than or equal to 15%, less than or equal to 14%, less than or equal to 13%, less than or equal to 12%, less than or equal to 11%, less than or equal to 10%, less than or equal to 9.0%, less than or equal to 8.0%, less than or equal to 7.0%, less than or equal to 6.0%, less than or equal to 5.0%, less than or equal to 4.5%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%) for light incident on the first layered film at angles of incidence of 60° or less ∘.

When viewed from the first layered film (i.e., from outside the LIDAR sensor), the windows described herein may exhibit reflection with CIELAB lightness L* values of less than or equal to 40 (e.g., less than or equal to 37, less than or equal to 35, less than or equal to 30) when viewed from angles of 60 degrees or less. The windows described herein may also exhibit reflection with CIELAB color space a* and b* values that are greater than or equal to −6 and less than or equal to 6 (e.g., greater than or equal to −5 and less than or equal to 5, greater than or equal to −4 and less than or equal to 4, greater than or equal to −3 and less than or equal to 3, greater than or equal to −2.5 and less than or equal to 2.5) when viewed from the first layered film when illuminated by an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. The perceived color of the window, when viewed from the side of the first layered film, may be black or relatively dark so as to render the window less noticeable to outside observers. In embodiments, the windows exhibit CIELAB color space a* and b* values that are greater than or equal to 2.5 and less than or equal to 2.5 when illuminated by an illuminant source at a plurality of different angles of incidence, ranging from 0° to 60.°

In further aspects, the windows described herein may be characterized in that they exhibit a relatively high transmittance (e.g., greater than or equal to 90%) over a 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest that is centered at a wavelength from 850 nm to 950 nm, while simultaneously exhibiting a relatively low average transmittance (e.g., less than or equal to 5%) in the visible spectrum (from 400 nm to 700 nm). Such contrasts in transmission at relatively close spectral ranges is achieved via incorporating absorber layers having relatively low extinction coefficients within the 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest. In embodiments, the absorber layers should have an extinction coefficient of less than or equal to 0.01 (e.g., less than or equal to 0.009, less than or equal to 0.008, less than or equal to 0.007, less than or equal to 0.005, less than or equal to 0.004, less than or equal to 0.0035, less than or equal to 0.0030, less than or equal to 0.0025, less than or equal to 0.0020, less than or equal to 0.0015, less than or equal to 0.0010) at a wavelength within a 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest between 850 nm and 950 nm. In embodiments, the absorber layers may simultaneously exhibit extinction coefficients in the visible spectrum that are relatively high (e.g., greater than or equal to 0.05, greater than or equal to 0.06, greater than or equal to 0.07, greater than or equal to 0.08) to absorb sufficient visible light to facilitate providing the dark, opaque appearance described herein. An example material for an absorber layer described herein is a silicon material having a low extinction coefficient over the 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest. When incorporated into the first and second layered films in the amounts described herein, such layers can absorb sufficient visible light to provide a suitable dark appearance, while also achieving the relatively high transmission within the 50 nm (or 60 nm, or 70 nm, or 80 nm, or 90 nm) wavelength range of interest in the near infrared.

As such, the windows described herein provide durable anti-reflection performance for a desired wavelength range of interest from 850 nm to 950 nm, while providing an aesthetically pleasing and performance enhancing black or dark appearance. The windows described herein may improve LIDAR sensor performance over certain existing sensors by preventing visible light from being incident on the sensors and improving signal-to-noise ratio. Moreover, the windows described herein may reduce unwanted glare that is visible to outside observers.

Unless otherwise noted, the total, specular, and average reflectance values provided herein are two-surface reflectance values, representing a total reflectance of an entire window, including the reflectance associated with each material interface in the window (e.g., between air and the layered films, between the layered films and the substrate, etc.). Unless otherwise noted, reflectance values provided in the infrared are measured from the side of the second layered film described herein (e.g., from the side positioned facing a sensor and emitter of a LIDAR system) and reflectance values provided in the visible are measured from the side of the first layered film described herein (e.g., from the side positioned facing an external environment of a LIDAR system).

Unless otherwise specified herein, average transmittance and reflectance values are calculated using percentage reflectance and transmittance values at various wavelengths within a specified wavelength range. Average reflectance transmittance values may be calculated by averaging values at each whole number wavelength within the specified wavelength range.

Unless otherwise noted herein, CIELAB color space a* and b* and lightness L* values are measured/simulated using a D65 illuminate for a standard observer with a 10-degree field of view.

As used herein, the terms “dark appearance” or “black appearance” refer to the reflected appearance of the window when viewed from an external surface. Windows having a dark appearance or black appearance in accordance with the present disclosure comprise average transmittance of 5% or less within 400-700 nm when viewed from 60° or less and reflection with CIELAB lightness L* values of less than 45 when viewed from angles 60° or less.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

Modifications of the disclosure will occur to those skilled in the art and to those who make or use the disclosure. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the disclosure, which is defined by the following claims, as interpreted according to the principles of patent law, including the doctrine of equivalents.

In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “Comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

The term “formed from” can mean one or more of comprises, consists essentially of, or consists of. For example, a component that is formed from a particular material can comprise the particular material, consist essentially of the particular material, or consist of the particular material.

As also used herein, the terms “article,” “glass-article,” “ceramic-article,” “glass-ceramics,” “glass elements,” “glass-ceramic article” and “glass-ceramic articles” may be used interchangeably, and in their broadest sense, to include any object made wholly or partly of glass and/or glass-ceramic material.

The term “disposed” is used herein to refer to a layer or sub-layer that is coated, deposited, formed, or otherwise provided onto a surface. The term disposed can include layers/sub-layers provided in direct contact with adjacent layers/sub-layers or layers/sub-layers separated by intervening material which may or may not form a layer.

Unless otherwise noted herein, refractive indices of the materials described herein are measured at 905 nm.

As used herein, the term “extinction coefficient” or “k” is a dimensionless property of a material that is dependent on a material's absorption coefficient, times a wavelength of light divided by 4π.

1 FIG. 10 12 12 10 12 14 10 16 10 Referring now to, a vehicleincludes one or more LIDAR systems. The one or more LIDAR systemscan be disposed anywhere on or within the vehicle. For example, the one or more LIDAR systemscan be disposed on a roofof the vehicleand/or a forward portionof the vehicle.

2 FIG. 12 18 20 18 22 Referring now to, each of the one or more LIDAR systemsinclude an electromagnetic radiation emitter and sensor, as known in the art, which may be enclosed in an enclosure. The electromagnetic radiation emitter and sensoremits electromagnetic radiationhaving a wavelength or range of wavelengths.

22 20 24 26 22 22 18 28 28 24 18 22 28 22 28 28 24 24 20 The emitted radiationexits the enclosurethrough a window, which is in the path of the emitted electromagnetic radiation. If an object (not illustrated) in an external environmentis in the path of the emitted radiation, the emitted radiationwill reflect off of the object and return to the electromagnetic radiation emitter and sensoras reflected radiation. The reflected radiationagain passes through the windowto reach the electromagnetic radiation emitter and sensor. In embodiments, the emitted radiationand the reflected radiationmay include light within a suitable wavelength range of interest. For example, in embodiments, the emitted radiationand reflected radiationmay be greater than or equal to 850 nm and less than or equal to 950 nm (e.g., greater than or equal to 875 nm and less than or equal to 925 nm, greater than or equal to 890 nm and less than or equal to 910 nm, approximately 905 nm, 905 nm). Electromagnetic radiation other than the reflected radiation(such as electromagnetic radiation having wavelengths in the visible spectrum, portions of the ultraviolet range) may also interact with the window. As described herein, the windowmay include layered films comprising layer structures that are designed to absorb light in the visible spectrum while also reflecting relatively low amounts of light in the visible spectrum, such that the window has a dark or black appearance when viewed from outside of the enclosure.

The “visible spectrum” is the portion of the electromagnetic spectrum that is visible to the human eye and generally refers to electromagnetic radiation having a wavelength within the range of about 400 nm to about 700 nm. The “ultraviolet range” is the portion of the electromagnetic spectrum having wavelengths between about 10 nm and about 400 nm. The “infrared range” of the electromagnetic spectrum begins at about 700 nm and extends to longer wavelengths. The sun generates solar electromagnetic radiation, commonly referred to as “sunlight,” having wavelengths that fall within all three of those ranges.

3 FIG. 24 12 30 30 32 34 32 34 30 32 26 34 18 22 34 32 28 32 34 30 36 32 30 38 34 30 24 24 Referring now to, the windowfor each of the one or more LIDAR systemsincludes a substrate. The substrateincludes a first surfaceand a second surface. The first surfaceand the second surfaceare the primary surfaces of the substrate. The first surfaceis closest to the external environment. The second surfaceis closest to the electromagnetic radiation emitter and sensor. The emitted radiationencounters the second surfacebefore the first surface. The reflected radiationencounters the first surfacebefore the second surface. The substratefurther includes a first layered filmdisposed on the first surfaceof the substrateand a second layered filmis disposed on the second surfaceof the substrate. It should be understood that the windowas described herein is not limited to vehicular applications, and can be used for whatever application the windowwould be useful to provide improved impact and optical performance, as described further herein.

30 30 30 The substratemay be constructed from a variety of different materials in accordance with the present disclosure. In embodiments, the substratemay be constructed of any type of glass, a glass ceramic, ceramic, or a suitable polymer-based material. Various example structures and compositions of the substrateare now described in greater detail.

30 30 30 In embodiments, the substrateincludes a glass composition or is a glass article. The substrate, for example, can include a borosilicate glass, an aluminosilicate glass, soda-lime glass, chemically strengthened borosilicate glass, chemically strengthened aluminosilicate glass, or chemically strengthened soda-lime glass. In embodiments, the glass composition of the substrateis capable of being chemically strengthened by an ion-exchange process. In embodiments, the composition may be free of lithium ions.

30 2 2 2 2 3 2 3 modifiers 2 2 3 2 3 2 2 2 3 2 3 modifiers An alkali aluminosilicate glass composition suitable for the substratecomprises alumina, at least one alkali metal and, In embodiments, greater than 50 mol. % SiO, in other embodiments at least 58 mol. % SiO, and in still other embodiments at least 60 mol. % SiO, wherein the ratio (AlO+BO)/Σ(i.e., sum of modifiers) is greater than 1, wherein the ratio of the components are expressed in mol. % and the modifiers are alkali metal oxides. This composition, in particular embodiments, comprises: 58-72 mol. % SiO; 9-17 mol. % AlO; 2-12 mol. % BO; 8-16 mol. % NaO; and 0-4 mol. % KO, wherein the ratio (AlO+BO)/Σ(i.e., sum of modifiers) is greater than 1.

30 2 2 2 3 2 3 2 3 2 2 3 2 2 2 2 2 3 2 3 2 2 3 2 2 2 3 Another suitable alkali aluminosilicate glass composition for the substratecomprises: 64-68 mol. % SiO; 12-16 mol. % NaO; 8-12 mol. % AlO; 0-3 mol. % BO; 2-5 mol. % KO4-6 mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol. %≤SiO+BO+CaO≤69 mol. %; NaO+KO+BO+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %; (NaO+BO)—AlO≤2 mol. %; 2 mol. %≤NaO—AlO≤6 mol. %; and 4 mol. %≤(NaO+KO)—AlO≤10 mol. %.

30 2 3 2 2 3 2 Another suitable alkali aluminosilicate glass composition for the substratecomprises: 2 mol. % or more of AlOand/or ZrO, or 4 mol. % or more of AlOand/or ZrO.

2 2 3 2 2 2 3 2 2 2 2 3 2 3 2 2 30 One example glass composition comprises SiO, BO, and NaO, where (SiO+BO)≥66 mol. %, and NaO≥9 mol. %. In an embodiment, the composition includes at least 6 wt. % aluminum oxide. In a further embodiment, the composition of one or more alkaline earth oxides, such as a content of alkaline earth oxides, is at least 5 wt. %. Suitable compositions, In embodiments, further comprise at least one of KO, MgO, and CaO. In a particular embodiment, the composition of the substratecomprises 61-75 mol. % SiO; 7-15 mol. % AlO; 0-12 mol. % BO; 9-21 mol. % NaO; 0-4 mol. % KO; 0-7 mol. % MgO; and 0-3 mol. % CaO.

30 2 2 3 2 3 2 2 2 2 2 2 2 3 2 3 2 2 2 A further example composition suitable for the substratecomprises: 60-70 mol. % SiO; 6-14 mol. % AlO; 0-15 mol. % BO; 0-15 mol. % LiO; 0-20 mol. % NaO; 0-10 mol. % KO; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO; 0-1 mol. % SnO; 0-1 mol. % CeO; less than 50 ppm AsO; and less than 50 ppm SbO; where 12 mol. %≤(LiO+NaO+KO)≤20 mol. % and 0 mol. %≤(MgO+CaO)≤10 mol. %.

30 2 2 3 2 3 2 2 2 2 2 2 2 3 2 3 2 2 2 A still further example glass composition suitable for the substratecomprises: 63.5-66.5 mol. % SiO; 8-12 mol. % AlO; 0-3 mol. % BO; 0-5 mol. % LiO; 8-18 mol. % NaO; 0-5 mol. % KO; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. % ZrO; 0.05-0.25 mol. % SnO; 0.05-0.5 mol. % CeO; less than 50 ppm AsO; and less than 50 ppm SbO; where 14 mol. %≤(LiO+NaO+KO)≤18 mol. % and 2 mol. %≤(MgO+CaO)≤7 mol. %.

30 30 24 30 30 30 24 The substratemay be substantially planar or sheet-like, although other embodiments may utilize a curved or otherwise shaped or sculpted substrate. The length and width of the substratecan vary according to the dimensions required for the window. The substratecan be formed using various methods, such as float glass processes and down-draw processes such as fusion draw and slot draw. The substratecan be used in a non-strengthened state. A commercially available example of a suitable non-strengthened substratefor the windowis Corning & glass code 2320, which is a sodium aluminosilicate glass substrate.

30 32 34 32 34 30 30 32 34 30 The glass forming the substratecan be modified to have a region contiguous with the first surfaceand/or a region contiguous with the second surfaceto be under compressive stress (“CS”). In such a circumstance, the region(s) under compressive stress extends from the first surfaceand/or the second surfaceto a depth(s) of compression. This generation of compressive stress further creates a central region that is under a tensile stress, having a maximum value at the center of the central region, referred to as central tension or center tension (CT). The central region extends between the depths of compression, and is under tensile stress. The tensile stress of the central region balances or counteracts the compressive stresses of the regions under compressive stress. As used herein, the terms “depth of compression” and “DOC” refer to the depth at which the stress within the substratechanges from compressive to tensile stress. At the depth of compression, the stress crosses from a positive (compressive) stress to a negative (tensile) stress and thus has a value of zero. The depth of compression protects the substratefrom the propagation of flaws introduced by sharp impact to the first and/or second surfaces,of the substrate, while the compressive stress minimizes the likelihood of a flaw growing and penetrating through the depths of compression. In embodiments, the depths of compression are each at least 20 μm. In embodiments, the absolute value of the maximum compressive stress CS within the regions is at least 200 MPa, at least about 400 MPa, at least 600 MPa, or up to about 1000 MPa.

30 Two methods for extracting detailed and precise stress profiles (stress as a function of depth) for a substratewith regions under compressive stress are disclosed in U.S. Pat. No. 9,140,543, entitled “Systems and Methods for Measuring the Stress Profile of Ion-Exchanged Glass,” filed by Douglas Clippinger Allan et al. on May 3, 2012, and claiming priority to U.S. Provisional Patent Application No. 61/489,800, having the same title, and filed on May 25, 2011, the contents of which are incorporated herein by reference in their entirety.

30 30 32 34 30 30 32 34 + + + + + + In embodiments, generating the region(s) of the substrateunder compressive stress includes subjecting the substrateto an ion-exchange chemical tempering process (chemical tempering is often referred to as “chemical strengthening”). In the ion-exchange chemical tempering process, ions at or near the first and second surfaces,of the substrateare replaced by—or exchanged with—larger ions usually having the same valence or oxidation state. In those embodiments in which the substratecomprises, consists essentially of, or consists of an alkali aluminosilicate glass, an alkali borosilicate glass, an alkali aluminoborosilicate glass, or an alkali silicate glass, ions in the surface layer of the glass and the larger ions are monovalent alkali metal cations, such as Na(when Liis present in the glass), K, Rb, and Cs. Alternatively, monovalent cations in, at, or near the first and second surfaces,may be replaced with monovalent cations other than alkali metal cations, such as Agor the like.

30 30 30 30 30 In embodiments, the ion-exchange process is carried out by immersing the substratein a molten salt bath containing the larger ions to be exchanged with the smaller ions in the substrate. It will be appreciated by those skilled in the art that parameters for the ion-exchange process, including, but not limited to, bath composition and temperature, immersion time, the number of immersions of the glass in a salt bath (or baths), use of multiple salt baths, and additional steps such as annealing, washing and the like, are generally determined by the composition of the substrateand the desired depths of compression and compressive stress of the substratethat result from the strengthening operation. By way of example, ion-exchange of alkali metal-containing glass substrates may be achieved by immersion in at least one molten bath containing a salt such as, but not limited to, nitrates, sulfates, and chlorides of the larger alkali metal ion. In embodiments, the molten salt bath comprises potassium nitrate (0-100 wt %), sodium nitrate (0-100 wt %), and lithium nitrate (0-12 wt %), the combined potassium nitrate and sodium nitrate having a weight percentage within the range of 88 wt % to 100 wt %. In embodiments, the temperature of the molten salt bath typically is in a range from about 350° C. up to about 500° C., while immersion times range from about 15 minutes up to about 40 hours, including from about 20 minutes to about 10 hours. However, temperatures and immersion times different from those described above may also be used. The substratemay be acid polished or otherwise treated to remove or reduce the effect of surface flaws.

30 In embodiments, the substrateincludes a glass-ceramic material having both a glassy phase and a ceramic phase. Illustrative glass-ceramics include those materials where the glass phase is formed from a silicate, borosilicate, aluminosilicate, or boroaluminosilicate, and the ceramic phase is formed from β-spodumene, β-quartz, nepheline, kalsilite, or carnegieite. “Glass-ceramics” include materials produced through controlled crystallization of glass. Examples of suitable glass-ceramics may include Li2O—Al2O3—SiO2 system (i.e., LAS-System) glass-ceramics, MgO—Al2O3-SiO2 system (i.e., MAS-System) glass-ceramics, ZnO×Al2O3×nSiO2 (i.e., ZAS system), and/or glass-ceramics that include a predominant crystal phase including β-quartz solid solution, β-spodumene, cordierite, and lithium disilicate. The glass-ceramic substrates may be strengthened using a chemical strengthening process.

30 In embodiments, the substrateincludes a ceramic material such as inorganic crystalline oxides, nitrides, carbides, oxy nitrides, carbo nitrides, and/or the like. Illustrative ceramics include those materials having an alumina, aluminum titanate, mullite, cordierite, zircon, spinel, perovskite, zirconia, ceria, silicon carbide, silicon nitride, silicon aluminum oxynitride, or zeolite phase.

30 In embodiments, the substrateincludes an organic or suitable polymeric material. Examples of suitable polymers include, without limitation: thermoplastics including polystyrene (PS) (including styrene copolymers and blends), polycarbonate (PC) (including copolymers and blends), polyesters (including copolymers and blends, including polyethyleneterephthalate and polyethyleneterephthalate copolymers), polyolefins (PO) and cyclicpolyolefins (cyclic-PO), polyvinylchloride (PVC), acrylic polymers including polymethyl methacrylate (PMMA) (including copolymers and blends), thermoplastic urethanes (TPU), polyetherimide (PEI) and blends of these polymers with each other. Other exemplary polymers include epoxy, styrenic, phenolic, melamine, and silicone resins.

30 30 30 30 In embodiments, the substrateincludes a plurality of layers or sub-layers. The layers or sub-layers of the substratemay be the same or different from one another. In embodiments, for example, the substratecomprises a glass laminate structure. In embodiments, the glass laminate structure comprises a first glass pane and a second pane attached to one another via a suitable interlayer (e.g., a polymer interlayer) disposed between the first glass pane and the second glass pane. In embodiments, the glass laminate structure comprises a glass-on-glass laminate structure formed via, for example, the fusion draw process. Glass-polymer laminates are also contemplated and within the scope of the present disclosure. Any material capable of meeting the optical requirements described herein may be used as the substrate.

30 In embodiments, the substrateexhibits an elastic modulus (or Young's modulus) in the range from about 30 GPa to about 120 GPa. In some instances, the clastic modulus of the substrate may be in the range from about 30 GPa to about 110 GPa, from about 30 GPa to about 100 GPa, from about 30 GPa to about 90 GPa, from about 30 GPa to about 80 GPa, from about 30 GPa to about 70 GPa, from about 40 GPa to about 120 GPa, from about 50 GPa to about 120 GPa, from about 60 GPa to about 120 GPa, from about 70 GPa to about 120 GPa, and all ranges and sub-ranges therebetween.

30 30 In embodiments, the substrateexhibits an average transmittance over the visible wavelength regime of about 85% or greater, about 86% or greater, about 87% or greater, about 88% or greater, about 89% or greater, about 90% or greater, about 91% or greater or about 92% or greater. In embodiments, the substratecomprises a tinting component (e.g., tinting layer or additive) and may optionally exhibit a color, such as white, black, red, blue, green, yellow, orange etc.

3 FIG. 30 35 32 34 35 30 30 35 35 35 35 As depicted in, the substratehas a thicknessdefined as the shortest straight-line distance between the first surfaceand the second surface. In embodiments, the thicknessof the substrateis between about 100 μm and about 5 mm. In embodiments, the substratecan have a physical thicknessranging from about 100 μm to about 500 μm (e.g., 100, 200, 300, 400, or 500 μm). In other embodiments, the thicknessranges from about 500 μm to about 1000 μm (e.g., 500, 600, 700, 800, 900, or 1000 μm). The thicknessmay be greater than about 1 mm (e.g., about 2, 3, 4, 5 mm, 6 mm, or 7 mm). In one or more specific embodiments, the thicknessis 2 mm or less or less than or equal to 1 mm.

35 35 35 30 35 30 30 30 30 In embodiments, the thicknessis uniform (e.g., varies by less than 1% throughout an entirety of the substrate) such that the substrateis in the form of a planar sheet. In embodiments, the thicknessis a variable thickness and has a value that varies as a function of position on the substrate. The thicknessmay vary along one or more of its dimensions for aesthetic and/or functional reasons. For example, the edges of the substratemay be thicker as compared to more central regions of the substrate. The length, width and physical thickness dimensions of the substratemay also vary according to the application or use of the article.

30 3143 1146 3143 In embodiments, the substrateincludes a visible light absorbing, IR-transmitting material layer. Examples of such materials include infrared transmitting, visible absorbing acrylic sheets, such as those commercially available from ePlastics under the trade names Plexiglas BIR acrylicand CYRO's ACRYLITE® IR acrylic. Plexiglas® IR acrylichas a transmissivity of about 0% (at least less than 10%, or less than 1%) for electromagnetic radiation having wavelengths of about 700 nm or shorter, but a transmissivity of about 90% (above 85%) for wavelengths within the range of 800 nm to about 1100 nm (including 905 nm).

30 In embodiments, the substrateexhibits a refractive index in the range from about 1.45 to about 1.55. In embodiments, the substrate exhibits an average transmission of greater than or equal to 95% (e.g., greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%) throughout a spectral range from 1400 nm to 1600 nm.

4 5 FIGS.and 36 38 40 42 40 42 36 38 40 42 Referring now to, the first layered filmand the second layered filmeach include a quantity of alternating layers of one or more higher refractive index materialsand one or more lower refractive index materials. While each of the one or more higher refractive index materialsand the one or more lower index materialsare identified using the same reference numerals, it should be understood that the utilization of the same reference numeral does not indicate that each of the layers are constructed of the same material or include the same structure. In each of the first and second layered filmsand, different ones of the layers of the respective higher refractive index materialsand the lower refractive index materialsmay include different compositional or structural properties.

40 42 40 42 42 40 40 42 40 42 24 36 36 38 40 42 As used herein, the terms “higher refractive index” and “lower refractive index” refer to the values of the refractive index relative to each other, with the refractive index/indices of the one or more higher refractive index materialsbeing greater than the refractive index/indices of the one or more lower refractive index materials. In embodiments, the one or more higher refractive index materialshave a refractive index from about 1.7 to about 4.5. In embodiments, the one or more lower refractive index materialshave a refractive index from about 1.3 to about 1.6. In embodiments, the one or more lower refractive index materialshave a refractive index from about 1.3 to about 1.7, while the one or more higher refractive index materialshave a refractive index from about 1.9 to about 3.8. The difference in the refractive index of any of the one or more higher refractive index materialsand any of the one or more lower refractive index materialsmay be about 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, 0.9 or greater, 1.0 or greater, 1.5 or greater, 2.0 or greater, 2.1 or greater, 2.2 or greater, or even 2.3 or greater. Because of the difference in the refractive indices of the one or more higher refractive index materialsand the one or more lower refractive index materials, manipulation of the quantity (number) of alternating layers and their thicknesses can cause selective transmission of electromagnetic radiation within a range of wavelengths through the windowand, separately, selective reflectance of electromagnetic radiation within a range of wavelengths off of the first layered film. The first layered film(and the second layered film, if utilized) is thus a thin-film optical filter having predetermined optical properties configured as a function of the quantity, thicknesses, number, and materials chosen as the one or more higher refractive index materialsand the one or more lower refractive index materials.

42 42 2 2 3 2 x y x y u v x y 2 4 2 2 2 3 3 3 3 x y x y u v x y Some examples of suitable materials for use as the one or more lower refractive index materialsinclude SiO, AlO, GeO, SiO, AlON, SiON, SiAlON, MgO, MgAlO, MgF, BaF, CaF, DyF, YbF, YF, and CeF. The nitrogen content of the materials for use as the one or more lower refractive index materialsmay be minimized (e.g., in materials such as AlON, SiON, and SiAlON).

40 40 40 40 40 42 40 42 42 40 x x y x u v x y 2 5 2 5 3 4 x y x y 2 2 2 2 3 2 3 3 x x x y x x x y u v x y 2 3 Some examples of suitable materials for use as the one or more higher refractive index materialsinclude Si, amorphous silicon (a-Si), SiN, SiN:H, AlN, SiAlON, TaO, NbO, AlN, SiN, AlON, SiON, HfO, TiO, ZrO, YO, AlO, MoO, and diamond-like carbon. The oxygen content of the materials for the higher refractive index materialmay be minimized, especially in SiNor AlNmaterials. AlONmaterials may be considered to be oxygen-doped AlN, that is they may have an AlNcrystal structure (e.g., wurtzite) and need not have an AlON crystal structure. Exemplary preferred AlONmaterials for use as the one or more higher refractive index materialsmay comprise from about 0 atom % to about 20 atom % oxygen, or from about 5 atom % to about 15 atom % oxygen, while including 30 atom % to about 50 atom % nitrogen. Exemplary preferred SiAlONfor use as the one or more higher refractive index materialsmay comprise from about 10 atom % to about 30 atom % or from about 15 atom % to about 25 atom % silicon, from about 20 atom % to about 40 atom % or from about 25 atom % to about 35 atom % aluminum, from about 0 atom % to about 20 atom % or from about 1 atom % to about 20 atom % oxygen, and from about 30 atom % to about 50 atom % nitrogen. The foregoing materials may be hydrogenated up to about 30% by weight. Because the refractive indices of the one or more higher refractive index materialsand the one or more lower refractive index materialsare relative to each other, the same material (such as AlO) can be appropriate for the one or more higher refractive index materialsdepending on the refractive index of the material(s) chosen for the one or more lower refractive index materials, and can alternatively be appropriate for the one or more lower refractive index materialsdepending on the refractive index of the material(s) chosen for the one or more higher refractive index material.

42 36 40 36 42 36 40 36 42 38 40 38 42 36 40 36 42 38 40 38 2 x y x 2 x x y 2 2 x x y 2 x x y In embodiments, the one or more lower refractive index materialsof the first layered filmconsists of layers of SiO, and the one or more higher refractive index materialsof the first layered filmconsists of layers of SiONor SiN. In embodiments, the one or more lower refractive index materialsof the first layered filmconsists of layers of SiO, and the one or more higher refractive index materialsof the first layered filmconsists of layers of SiNor SiON, while the one or more lower refractive index materialsof the second layered filmconsists of layers of SiOand the one or more higher refractive index materialsof the second layered filmcomprises layers of silicon (e.g., a-Si). In embodiments, the one or more lower refractive index materialsof the first layered filmconsists of layers of SiO, and the one or more higher refractive index materialsof the first layered filmconsists of layers of SiNor SiON, while the one or more lower refractive index materialsof the second layered filmconsists of layers of SiOand the one or more higher refractive index materialsof the second layered filmcomprises layers of amorphous silicon (a-Si) and layers of SiNor SiON.

40 42 36 38 36 38 36 38 24 30 36 38 24 The quantity of alternating layers of the higher refractive index materialand the lower refractive index materialin either the first layered filmor the second layered filmis not particularly limited. In embodiments, the number of alternating layers within the first layered filmis 7 or more, 9 or more, 11 or more, 13 or more, 15 or more, 17 or more, 19 or more, 21 or more, 23 or more, 25 or more, or 51 or more, or 81 or more. In embodiments, the quantity of alternating layers within the second layered filmis 7 or more, 9 or more, 11 or more, 13 or more, 15 or more, 17 or more, 19 or more, 21 or more, 23 or more, or 25 or more, or 51 or more, or 81 or more. In embodiments, the quantity of alternating layers in the first layered filmand the second layered filmcollectively forming the window, not including the substrate, is 14 or more, 20 or more, 26 or more, 32 or more, 38 or more, 44 or more, 50 or more, 72 or more, or 100 or more. In general, the greater the quantity of layers within the first layered filmand the second layered film, the more narrowly the transmittance and reflectance properties of the windoware tailored to one or more specific wavelengths or wavelength ranges.

36 38 24 24 40 42 24 Each of the alternating layers of the first layered filmand the second layered filmhas a thickness. The thicknesses selected for each of the alternating layers determines the optical path lengths of light propagating through the windowand determines the constructive and destructive interference between different light rays reflected at each material interface of the window. Accordingly, the thicknesses of each of the alternating layers, in combination with the refractive index of the one or more higher refractive index materialsand the one or more lower refractive index materialsdetermines the reflectance and transmittance spectra of the window.

3 4 5 FIGS.,, and 28 44 36 24 44 26 42 44 26 28 44 42 44 36 30 42 42 32 30 30 42 2 2 2 2 With reference to, the reflected radiationfirst encounters a terminal surfaceof the first layered filmupon interacting with the window, and the terminal surfacemay be open to the external environment. In an embodiment, a layer of the one or more lower refractive index materialsprovides the terminal surfaceto more closely match the refractive index of the air in the external environmentand thus reduce reflection of incident electromagnetic radiation (whether the reflected radiationor otherwise) off of the terminal surface. The layer of the one or more lower refractive index materialsthat provides the terminal surfaceis the layer of the first layered filmthat is farthest from the substrate. Similarly, in embodiments, when the one or more lower refractive index materialsis SiO, a layer of SiO, as the one or more lower refractive index materials, is disposed directly onto the first surfaceof the substrate, which will typically comprise a large mole percentage of SiO. Without being bound by theory, it is thought that commonality of SiOin both the substrateand the adjacent layer of the one or more lower refractive index materialsallows for increased bonding strength.

22 48 38 24 42 48 20 22 48 42 48 38 30 42 42 34 30 2 2 The emitted radiationfirst encounters a terminal surfaceof the second layered filmupon interacting with the window. In an embodiment, a layer of the one or more lower refractive materialsprovides the terminal surfaceto more closely match the refractive index of the air within the enclosureand thus reduce reflection of the incident emitted radiationoff of the terminal surface. The layer of the one or more lower refractive index materialsthat provides the terminal surfaceis the layer of the second layered filmthat is farthest from the substrate. Similarly, in embodiments, when the one or more lower refractive index materialsis SiO, a layer of SiO, as the one or more lower refractive index materials, is disposed directly onto the second surfaceof the substrate.

40 40 24 36 26 36 40 x y x x y 3 4 x y Materials that have a relatively high refractive index can simultaneously have a relatively high hardness that provides scratch and impact resistance. An example material that has both high hardness and can be one of the one or more higher refractive index materialis SiON. Other example materials that have both high hardness and can be the higher refractive index materialare SiN, SiN:H, and SiN. It has been found that a relatively thick (e.g., greater than or equal to 500 nm) layer of SiON(or other suitable higher refractive index material) may increase the scratch and/or damage resistance of the window. Such increased scratch and/or damage resistance may be particularly beneficial in the first layered film, which may be more likely to encounter impacts of debris from the external environment. Accordingly, in embodiments, the first layered filmcomprises a layer of one of the one or more higher refractive index materialswith a thickness greater than or equal to 500 nm (e.g., greater than or equal to 1000 nm, greater than or equal to 1500 nm, greater than or equal to 2000 nm). Such a higher refractive index layer having such a thickness of 500 nm or more is described herein as a “scratch resistant layer.”

36 36 24 24 40 24 24 12 10 40 24 12 40 24 40 36 40 24 36 26 38 20 In embodiments, the thickness and location within the first layered filmof the scratch resistant layer can be optimized to provide a desired level of hardness and scratch resistance to the first layered filmand thus the windowas a whole. Different applications of the windowcould lead to different desired thicknesses for the scratch resistant layer of the higher refractive index materialserving as the layer providing the hardness and scratch resistance to the window. For example, a windowprotecting a LIDAR systemon a vehiclemay require a different thickness for the scratch resistant layer of the higher refractive index materialthan a windowprotecting a LIDAR systemat an office building. In embodiments, the scratch resistant layer of the higher refractive index materialserving as the layer providing the hardness and scratch resistance to the windowhas a thickness between 500 nm and 50000 nm, such as between 500 nm and 10000 nm, such as between 2000 nm to 5000 nm. In embodiments, the thickness of this scratch resistant layer of higher refractive index materialhas a thickness that is 30% or more, 40% or more, 50% or more, 65% or more, or 85% or more, or 86% or more, of the thickness of the first layered film. In general, the scratch resistant layer of the higher refractive index materialserving as the layer providing the hardness and scratch resistance to the windowwill be part of the first layered filmfacing the external environmentrather the second layered filmprotected by the enclosure, although that may not always be so.

36 38 24 40 24 24 40 24 3 4 As will be detailed further below, the quantity, thicknesses, number, and materials of the remaining layers of the first layered filmand the second layered filmcan be configured to provide the windowwith the desired optical properties (transmittance and reflectance of desired wavelengths) almost regardless of the thickness chosen for the scratch resistant layer of the higher refractive index materialserving as the layer providing the hardness and scratch resistance to the window. This insensitivity of the optical properties of the windowas a whole to the thickness of the scratch resistant layer of the higher refractive index materialserving as the layer providing the hardness and scratch resistance to the windowwhen materials having relatively low or negligible optical absorption of electromagnetic radiation of the target wavelength or wavelength range (e.g., from 850 nm to 950 nm, 905 nm). For example, SiNonly negligibly absorbs electromagnetic radiation in the 700 nm to 2000 nm wavelength range.

40 36 36 24 14 10 36 24 16 10 40 36 This general insensitivity allows the scratch resistant layer of the higher refractive index materialin the first layered filmto have a thickness predetermined to meet specified hardness or scratch resistance requirements. For example, the first layered filmfor the windowutilized at the roofof the vehiclemay have different hardness and scratch resistance requirements than the first layered filmfor the windowutilized at the forward portionof the vehicle, and thus a different thickness for the scratch resistant layer of the higher refractive index material. This can be achieved without significant altering of the transmittance and reflectance properties of the first layered filmas a whole.

36 24 40 24 36 40 44 44 36 36 24 12 10 12 1 FIG. The hardness of the first layered film, and thus the window, with the scratch resistant layer of the higher refractive index materialcan be quantified. In embodiments, the maximum hardness of the window, measured at the first layered filmwith the scratch resistant layer of the higher refractive index material, as measured by the Berkovich Indenter Hardness Test, may be about 8 GPa or greater, about 10 GPa or greater, about 12 GPa or greater, about 14 GPa or greater, about 15 GPa or greater, about 16 GPa or greater, or about 18 GPa or greater at one or more indentation depths from 50 nm to 2000 nm (measured from the terminal surface), and even from 2000 nm to 5000 nm. As used herein, the “Berkovich Indenter Hardness Test” includes measuring the hardness of a material on a surface thereof by indenting the surface with a diamond Berkovich indenter. The Berkovich Indenter Hardness Test includes indenting the terminal surfaceof the first layered filmwith the diamond Berkovich indenter to form an indent to an indentation depth in the range from about 50 nm to about 2000 nm (or the entire thickness of the first layered film) and measuring the maximum hardness from this indentation along the entire indentation depth range or a segment of this indentation depth range (e.g., in the range from about 100 nm to about 600 nm), generally using the methods set forth in Oliver, W. C.; Pharr, G. M. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res., Vol. 7, No. 6, 1992, 1564-1583; and Oliver, W. C.; Pharr, G. M. Measurement of Hardness and Elastic Modulus by Instrument Indentation: Advances in Understanding and Refinements to Methodology. J. Mater. Res., Vol. 19, No. 1, 2004, 3-20. These levels of hardness improve the resistance of the windowto impact damage from sand, small stones, debris, and other objects encountered while the LIDAR systemis used for its intended purpose, such as with the vehicle(see). Accordingly, these levels of hardness reduce or prevent the optical scattering and reduced performance of the LIDAR systemthat the impact damage would otherwise cause.

36 40 44 36 42 40 44 44 44 12 36 In embodiments, at least a portion of the first layered filmis disposed between the scratch resistant layer of the higher refractive index materialand the terminal surface. In embodiments, the first layered filmcomprises a plurality of alternating layers of the one or more lower refractive index materialsand the one or more higher refractive index materialsbetween the terminal surfaceand the scratch resistant layers. Such a stack of alternating layers disposed between the scratch resistant layer and the terminal surfaceis described herein as the “optical control layers.” In embodiments, the optical control layers, disposed between the scratch resistant layer and the terminal surface, have a combined thickness of greater than or equal to 500 nm (e.g., greater than or equal to 600 nm, greater than or equal to 700 nm, greater than or equal to 800 nm, greater than or equal to 900 nm, greater than or equal to 1000 nm, greater than or equal to 1100 nm, greater than or equal to 1200 nm, greater than or equal to 1300 nm). The quantity, composition, and thickness of the optical control layers may be selected to provide desired anti-reflection performance attributes described herein at an operational wavelength of the LIDAR sensorbetween 850 nm and 950 nm. That way, the second layered filmmay be designed to provide desirable optical performance characteristics in the visible and/or UV spectrum, as described herein.

46 36 44 36 36 36 36 36 36 36 36 36 In embodiments, at least 25% (e.g., at least 26%, at least 27%, at least 28%, at least 29%, at least 30%) of a thicknessof the first layered filmis disposed between the scratch resistant layer and the terminal surface. It is believed that such a depth of the scratch resistant layer within the first layered filmfacilitates the first layered filmhaving a relatively high nanoindentation hardness (as measured by the Berkovich Indenter Hardness Test) over a relatively large range of depths within the first layered film. In embodiments, the first layered filmhas a nanoindentation hardness of greater than or equal to 8 GPa from a depth of 50 nm to a depth of 2000 nm within the first layered film. In embodiments, the first layered filmhas a nanoindentation hardness of greater than or equal to 10 GPa from a depth of 100 nm to a depth of 1000 nm within the first layered film. In embodiments, the first layered filmhas a nanoindentation hardness of greater than or equal to 14 GPa from a depth of 400 nm to a depth of 1000 nm within the first layered film. Such hardness values facilitate providing scratch and/or damage resistance against flaws having a relatively wide range of depths.

4 5 FIGS.and 36 46 38 50 46 36 40 46 46 24 46 36 30 46 36 30 30 50 38 24 50 38 Referring now to, the first layered filmhas a thickness, and the second layered filmhas a thickness. The thicknessof the first layered film, assumed to include the scratch resistant layer of the one or more higher refractive index materials, may be about 1 μm or greater while still providing the transmittance and reflectance properties described herein. In embodiments, the thicknessis in the range of 1 μm to just over 50 μm, including from about 1 μm to about 10 μm, and from about 2800 nm to about 5900 nm. The lower bound of about 1 μm is approximately the minimum thicknessthat still provides hardness and scratch resistance to the window. The higher bound of thicknessis limited by cost and time required to dispose the layers of the first layered filmonto the substrate. In addition, the higher bound of the thicknessis limited to prevent the first layered filmfrom warping the substrate, which is dependent upon the thickness of the substrate. The thicknessof the second layered filmcan be any thickness deemed necessary to impart the windowwith the desired transmittance and reflectance properties. In embodiments, the thicknessof the second layered filmis in the range of about 800 nm to about 7000 nm.

24 40 36 24 36 38 24 32 34 32 34 While solving the problem discussed above in the background through imparting hardness, impact, and scratch resistance to the windowvia the maximized thickness of a higher refractive index material, the quantity, thicknesses, number, and materials of the layers of the first layered filmand the second layered film are configured to also provide a relatively high transmittance of infrared radiation between 850 nm and 950 nm through the window. In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the windowhas an average percentage transmittance, calculated over a 50 nm wavelength range of interest centered at a wavelength from 850 nm to 950 nm (e.g., a 20 nm wavelength range of interest centered at 905 nm) of greater than or equal to 90% (e.g., greater than or equal to 91%, greater than or equal to 92%, greater than or equal to 93%, greater than or equal to 94%, greater than or equal to 95%) for light incident on the first surfaceand the second surfaceat angles within 15° of normal to the first surfaceand the second surface.

36 38 24 32 34 32 34 36 38 32 34 32 34 24 30 36 38 In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the windowhas an average reflectance, calculated over a 50 nm wavelength range of interest centered at a wavelength from 850 nm to 950 nm (e.g., a 20 nm wavelength range of interest centered at 905 nm), of less than or equal to 4.0% (e.g., less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%, less than or equal to 1.5%, less than or equal to 1.0%) for light incident on the first surfaceand the second surfaceat angles within 15° of normal to the first surfaceand the second surface. In embodiments, the number, thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over a 50 nm wavelength range of interest centered at a wavelength from 850 nm to 950 nm (e.g., a 20 nm wavelength range of interest centered at 905 nm), of greater than 85% (e.g., greater than or equal to 86%, greater than or equal to 87%, greater than or equal to 88%, greater than or equal to 89%, greater than or equal to 90%, greater than or equal to 91%, greater than or equal to 92%) for light incident on the first surfaceand the secondsurface at angles within 60° of normal (e.g., at angles of incidence from 0° to 60°, from 0° to 50°, from 0° to 40°, from 0° to) 30° to the first surfaceand the second surface. Herein, the term “reflectance” is defined as the percentage of incident optical power within a given wavelength range that is reflected from a material (e.g., the window, the substrate, the first layered film, second layered film, or portions thereof).

36 38 24 32 34 24 30 36 38 In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the windowhas an average percentage transmittance, calculated over a 50 nm wavelength range of interest centered at a wavelength from 850 nm to 950 nm (e.g., a 20 nm wavelength range of interest centered at 905 nm), of greater than or equal to 95% (e.g., greater than or equal to 95.5%, greater than or equal to 96%, greater than or equal to 96.5%, greater than or equal to 97.5%, greater than or equal to 98%) for light normally incident on the first surfaceand the second surface. Herein, the term “transmittance” and “percentage transmission” are used interchangeably ad refer to the percentage of incident optical power within a given wavelength range transmitted through a material (e.g., the window, the substrate, the first layered film, the second layered filmor portions thereof).

36 38 24 26 24 32 24 32 30 1 FIG. In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the windowalso (in addition to meeting the optical performance requirements in the infrared described herein) has a desired dark appearance. For example, when viewed from the external environment(see), the windowmay exhibit CIELAB color space a* values that are greater than or equal to −6.0 and less than or equal to 6.0 (e.g., greater than or equal to −5.0 and less than or equal to 5.0, greater than or equal to −4.0 and less than or equal to 4.0, greater than or equal to −3.0 and less than or equal to 3.0, greater than or equal to −2.5 and less than or equal to 2.5, greater than or equal to −2.5 and less than or equal to 0) for light having angles of incidence on the first surfaceranging from 0° to 90°. The windowmay also exhibit CIELAB color space b* values that are greater than or equal to −6.0 and less than or equal to 6.0 (e.g., greater than or equal to −5.0 and less than or equal to 5.0, greater than or equal to −4.0 and less than or equal to 4.0, greater than or equal to −3.0 and less than or equal to 3.0, greater than or equal to −2.5 and less than or equal to 2.5, greater than or equal to −2.5 and less than or equal to 0) for light having angles of incidence on the first surfaceranging from 0° to 90°. Such color space values may be obtained even in embodiments where the substrateis has a relatively high transmittance (e.g., greater than 90%) and low reflectance (e.g., less than or equal to 22%) throughout the visible spectrum.

36 38 24 36 38 24 36 24 In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the windowhas a CIELAB lightness L* value of less than 45 (e.g., less than or equal to 40, less than or equal to 35, less than or equal to 30) when viewed from angles of incidence of less than or equal to 60°. In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered filmsandare configured so that the windowhas a CIELAB lightness L* value of less than 20 for light that is normally incident on the first layered filmand reflected. The aforementioned combination of CIELAB color space and lightness values represent that the windowhas a relatively dark appearance from a variety of angles of incidence.

24 40 38 36 38 24 38 40 36 30 26 36 38 The dark appearance of the windowmay be achieved by incorporating silicon (e.g., as a-Si) or other suitable material that absorbs in the visible spectrum (herein referred to as “absorber layer”) as one of the one or more higher refractive index materialsin the second layered film. Silicon is suitable for an absorber layer because, in addition to having a relatively high refractive index (approximately 4.0 at 905), silicon has a relatively high optical absorption in the ultraviolet range and visible light range. The thicknesses and quantity of layers of silicon, along with the other layers of the first layered filmand second layered filmcan thus provide a windowwith low percentage transmittance of electromagnetic radiation in the ultraviolet range and visible light range (due in part to the optical absorbance of the amorphous at those wavelength ranges) but high percentage transmittance in the desired portions of the infrared range. In embodiments, the second layered filmincludes one or more layers of silicon (e.g., as a-Si) as one of the one or more higher refractive index materialswhile the first layered filmdoes not. Such a structure may be beneficial in that silicon is solely located behind the substrateand thus protected from the external environment. As a result, the nanoindentation hardness values described herein may be obtained via incorporation of the scratch resistance layer into the first layered filmwhile the dark appearance may be obtained via incorporation of silicon into the second layered film.

40 40 18 In embodiments, the silicon material used to form at least one of the one or more layer of higher refractive materialsis modified to facilitate achieving relatively high optical transmittance over the 50 nm wavelength of interest centered about a wavelength from 850 nm to 950 nm. Particularly, it has been found that the silicon material (or other suitable material that absorbs more radiation in the visible spectrum at higher amounts than the other higher index materialsdescribed herein) should have an extinction coefficient of less than or equal to 0.01 (e.g., less than or equal to 0.009, less than or equal to 0.008, less than or equal to 0.007, less than or equal to 0.005, less than or equal to 0.004, less than or equal to 0.0035, less than or equal to 0.0030, less than or equal to 0.0025, less than or equal to 0.0020, less than or equal to 0.0015, less than or equal to 0.0010) at a wavelength within the wavelength range of interest (the wavelength may range from 890 nm to 910 nm in some embodiments, and, in various embodiments, be approximately 890 nm, 891 nm, 892 nm, 893 nm, 894 nm, 895 nm, 896 nm, 897 nm, 898 nm, 899 nm, 900 nm, 901 nm, 902 nm, 903 nm, 904 nm, 905 nm, 906 nm, 907 nm, 908 nm, 909 nm, and 910 nm, and any and all ranges including any of these values as endpoints, with the wavelength to a peak operating wavelength associated with at least one of the emitter and sensor). In embodiments, it is preferrable that the silicon material have an extinction coefficient of less than 0.005 at the wavelength, while simultaneously exhibiting a relatively higher extinction coefficient (e.g., greater than or equal to 0.06 greater than or equal to 0.07, greater than or equal to 0.08, greater than or equal to 0.09, greater than or equal to 0.1) throughout the visible spectrum. Such low extinction coefficient within the 50 nm wavelength range of interest and relatively high extinction coefficient throughout the visible spectrum facilitates adding silicon in sufficient amounts to reduce visible transmission to the ranges described herein without significantly effecting the transmittance within the wavelength range of interest.

38 50 50 24 32 34 32 34 28 18 12 2 FIG. In embodiments, the alternating layers of the second layered filmformed of silicon have a combined thickness of greater than or equal to 250 nm (e.g., greater than or equal to 300 nm, greater than or equal to 325 nm, greater than or equal to 350 nm, greater than or equal to 375 nm, greater than or equal to 400 nm, greater than or equal to 450 nm, greater than or equal to 500 nm, greater than or equal to 550 nm, greater than or equal to 600 nm, greater than or equal to 650 nm, greater than or equal to 700 nm). In embodiments, the combined thickness of the silicon layers in the second layered film constitutes at least 20% (e.g., at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%) of the thicknessof the second layered film. Applicant has found that such a thickness of silicon sufficiently absorbs visible light such that the windowpossess an average percentage transmission, calculated from 400 nm to 700 nm, of less than 5% (e.g., less than or equal to 4.5%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%, less than or equal to 1.5%, less than or equal to 1.0% less than or equal to 0.9%, less than or equal to 0.8%, less than or equal to 0.7%, less than or equal to 0.6%, less than or equal to 0.5%, less than or equal to 0.4%, less than or equal to 0.3%, less than or equal to 0.2%, less than or equal to 0.1%) for light incident on the first surfaceand the second surfaceat angles within 15° of normal to the first surfaceand the second surface. As such, portions of the reflected radiation(see) containing visible light do not reach the emitter and sensor, thereby improving the signal-to-noise ratio of the LIDAR system.

36 36 38 34 38 34 30 In embodiments, the second layered filmcomprises two or more layers formed from silicon. In embodiments, at least one of the two or more layers formed from silicon comprises a thickness of greater than or equal to 150 nm (e.g., greater than or equal to 160 nm, greater than or equal to 170 nm, greater than or equal to 180 nm, greater than or equal to 190 nm, greater than or equal to 200 nm). In embodiments, at least two, but less than all, of the two or more layers formed from silicon in the second layered filmcomprises thicknesses of greater than or equal to 150 nm. In embodiments, at least seven (7) of the alternating layers of the second layered filmare disposed between one of the silicon layers having a thickness of 150 nm or more and the second surface. In embodiments, silicon layers contained in the second layered filmcomprising thicknesses that are less than 150 nm from the second surfacecomprise thicknesses of less than or equal to 70 nm (e.g., less than or equal to 65 nm, less than or equal to 60 nm, less than or equal to 55 nm, less than or equal to 50 nm, less than or equal to 30 nm, less than or equal to 25 nm, less than or equal to 20 nm). It is believed that such separation between the substrateand the relatively thick silicon layers aids in reducing reflectance in the visible spectrum.

36 38 24 26 1 FIG. In embodiments, the alternating layers of the first and second layered filmsandare constructed to achieve a relatively low average reflectance in the visible spectrum. For example, in embodiments, the window comprises an average reflectance, computed in a wavelength range from 400 nm to 700 nm, of less than or equal to 10% (e.g., less than or equal to 9%, less than or equal to 8%, less than or equal to 7%). Such low reflectance beneficially prevents the windowfrom having a tinted appearance when viewed from the external environment(see) and facilitates achieving the CIE color space a* and b*, and lightness L* values described herein.

38 30 38 38 40 30 38 38 In embodiments, to limit the reflectance in the visible spectrum of the window, a silicon layer of the second layered filmmost proximate to the substrateis the narrowest silicon layer in the second layered film. That is, of the layers in the second layered filmwhere the one or more higher refractive index materialsis silicon, the closest one to the substratecomprises the least thickness. In embodiments, the nearest silicon layer in the second layered filmcomprises a thickness that is less than or equal to 15 nm (e.g., less than or equal to 10 nm, less than or equal to 8 nm, less than or equal to 7 nm, less than or equal to 6 nm, less than or equal to 5 nm, less than or equal to 4 nm, less than or equal to 3 nm, less than or equal to 2 nm). Applicant has found that such structure beneficially prevents the silicon-containing layers in the second layered filmfrom inducing a tinted reflectance, while still contributing to the relatively low visible transmittance values described herein.

40 30 38 40 30 40 30 38 38 38 x x y 3 4 In embodiments, the layer of the one or more higher refractive index materialsthat is closest to the substratein the second layered filmis not silicon. In embodiments, for example, the layer of the one or more higher refractive index materialsthat is closest to the substratemay be constructed of the same higher refractive index material used in the first layered film (e.g., SiN, SiON, SiN). In embodiments, the layer of the one or more higher refractive index materialsthat is closest to the substratein the second layered filmis the only higher index layer therein that is not constructed of silicon. Without wishing to be bound by theory, Applicant believes that such a structure may aid in reducing reflectance in the visible spectrum when incorporating silicon into the second layered film, especially when the silicon layers contained in the second layered filmcomprise thicknesses greater than or equal to 8 nm.

36 38 40 42 The layers of the first layered filmand the second layered film(i.e., layers of the higher refractive index materialand the lower refractive index material) may be formed by any known method in the art, including discrete deposition or continuous deposition processes. In one or more embodiments, the layer may be formed using only continuous deposition processes, or, alternatively, only discrete deposition processes.

36 38 24 The following examples are all modeled examples using computer facilitated modeling to demonstrate how the quantity, thicknesses, number, and materials of the layers of the first layered filmand the second layered filmcan be configured so that the windowhas a desired average percentage transmittance and average percentage reflectance as a function of the wavelength and angle of incidence of the incident electromagnetic radiation.

24 36 38 38 6 6 FIGS.A-B 6 FIG.A Example 1—the windowof Example 1 included a first layered filmand a second layered film. The second layered filmincluded layers of a silicon material having represented as the “Low k” material in. The Low k material was supported amorphous silicon and formed via a similar method as the existing material, but process conditions were altered during the deposition process. As shown, the Low k material exhibits an extinction coefficient that is shifted downward from that of certain existing silicon materials throughout the wavelength range of 350 nm to 1000 nm. As a result, the Low k material exhibits have an extinction coefficient of less than or equal to 0.01 (e.g., in this specific example, less than or equal to 0.004) throughout the wavelength range of 850 nm to 950 nm. Throughout the wavelength range of 890 nm to 910 nm, the Low k silicon exhibits an extinction coefficient of less than 0.002 (approximately 0.0016 at 905 nm). This is a reduction of over an order of magnitude as compared to the existing silicon material, which had extinction coefficients greater than or equal to 0.044 throughout the wavelength range of 850 nm to 950 nm. Moreover, as shown in, the extinction coefficient of the Low k material is comparable (differs by less than an order of magnitude) to that of the existing silicon material over the wavelength range of 400 nm to 700 nm. From 400 nm to 700 nm, the Low k material exhibits an extinction coefficient ranging from 0.078 to 1.92. Such relatively high extinction coefficients within the visible spectrum enables the Low k silicon material to be incorporated in sufficient quantities to absorb visible light and provide the dark, opaque appearance described herein, while the relatively low extinction coefficient allows such quantities to be introduced without adversely effecting transmission in the 50 nm wavelength range of interest to a significant degree.

24 36 32 30 24 38 34 30 36 42 40 40 44 32 36 2 The windowof Example 1 included a first layered filmover a first surfaceof a substrateof an aluminosilicate glass (Corning code 2320). The windowalso included a second layered filmover a second surfaceof the substrate. The first layered filmincluded thirty-three (33) alternating layers of SiOas the lower refractive index materialand SiN as the higher refractive index material. Layer 24 was the scratch resistant layer of the higher refractive index material, having a thickness of 2000 nm. Layers 1-23 were optical control layers having a combined thickness of 1307.01 nm separating the scratch resistant layer from the terminal surface. Layers 25-33 were index matching layers separating the scratch resistance layer from the first surfaceand having a combined thickness of 338.45 nm. In this example, the scratch resistant layer constituted 54.86% of the thickness of the first layered film.

38 42 40 42 40 40 30 40 30 38 2 The second layered filmincluded twenty-three (23) alternating layers of the lower refractive index materialand the higher refractive index material. In this example, the lower refractive index materialwas SiO, while the higher refractive index materialwas a combination of SiN and Si. As shown, layers 35, 37, 39, and 41—the four closest layers of the higher refractive index materialto the substrate—were SiN, while the remaining layers of the higher refractive index materialwere the Low k Si. Layer 43—the Si layer most proximate to the substrate—was the narrowest Si layer, with a thickness of 12.04 nm. The combined thickness of the silicon layers was 708.4 nm, which constituted 46.6% of the total thickness of the second layered film.

36 38 7 12 FIGS.- The thicknesses of the layers of the first layered filmand the second layered filmwere configured as set forth in Table 1 below and used to calculate the transmittance, reflectance. CIELAB color space and lightness values of reflection, and nanoindentation hardness values set forth in.

TABLE 1 Example 1 Layer Design Refractive Physical Index Thickness Layer Material @905 nm (nm) Medium Air 1 Perfluoropolyether 1-4 4-8 1 SiO2 1.4603 117.94 2 SiN 2.0669 30.77 3 SiO2 1.4603 19.42 4 SiN 2.0669 97.14 5 SiO2 1.4603 22.98 6 SiN 2.0669 23.02 7 SiO2 1.4603 191.56 8 SiN 2.0669 19.36 9 SiO2 1.4603 30.73 10 SiN 2.0669 159.88 11 SiO2 1.4603 31.34 12 SiN 2.0669 26.75 13 SiO2 1.4603 93.35 14 SiN 2.0669 8.24 15 SiO2 1.4603 83.77 16 SiN 2.0669 25.05 17 SiO2 1.4603 28.03 18 SiN 2.0669 38.6 19 SiO2 1.4603 12.14 20 SiN 2.0669 170.54 21 SiO2 1.4603 11.77 22 SiN 2.0669 52.41 23 SiO2 1.4603 12.22 24 SiN 2.0669 2000 25 SiO2 1.4603 16.07 26 SiN 2.0669 47.91 27 SiO2 1.4603 37.02 28 SiN 2.0669 34.66 29 SiO2 1.4603 65.63 30 SiN 2.0669 17.73 31 SiO2 1.4603 85.09 32 SiN 2.0669 9.34 33 SiO2 1.4603 25 Substrate Aluminosilicate glass (2320) 1.4916 2000000 34 SiO2 1.4603 25 35 SiN 2.0669 19.88 36 SiO2 1.4603 37.66 37 SiN 2.0669 48.5 38 SiO2 1.4603 16.37 39 SiN 2.0669 187.7 40 SiO2 1.4603 23.07 41 SiN 2.0669 63.06 42 SiO2 1.4603 15.3 43 Si 3.6748 12.04 44 SiO2 1.4603 21.17 45 Si 3.6748 27.79 46 SiO2 1.4603 11.08 47 Si 3.6748 104.41 48 SiO2 1.4603 17.2 49 Si 3.6748 186.33 50 SiO2 1.4603 8.1 51 Si 3.6748 182.97 52 SiO2 1.4603 14.5 53 Si 3.6748 169.94 54 SiO2 1.4603 62.22 55 Si 3.6748 24.92 56 SiO2 1.4603 240.11 Medium Air 1

7 FIG. 7 FIG. 8 FIG. 24 24 36 38 24 32 34 36 38 24 is a plot of a modelled transmittance of the windowaccording to Example 1 of light that is incident on the windowat a 15° angle of incidence throughout the spectral range of 850 nm to 950 nm. As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 1 has a percentage transmittance of above 93 percent for light incident on the first surfaceor the second surfaceat angles of incidence of less than 15° throughout a wavelength range extending from 850 nm to 950 nm. Indeed, throughout the wavelength range of 850 nm to 950 nm, the window exhibits a transmittance of greater than 93% for light at a 15° angle of incidence. The transmittance is greater than 95% throughout the wavelength range of 860 nm to 950 nm. At 905 nm, the transmittance is about 97%. As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 1 has an average P polarization transmittance and an average S polarization transmittance, calculated a wavelength range of interest from 850 nm to 950 nm, of greater than 89% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface. Throughout the wavelength range of 890 nm to 910 nm, the S and P polarization transmittances are greater than 91%.

9 FIG. 36 38 24 44 36 48 38 300 44 48 36 38 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 1 has a percentage reflectance off of the terminal surfaceof the first layered filmand the terminal surfaceof the second layered filmof under 4 percent for light incident on the substrateat an angle of incidence of 15° within the approximate wavelength range of 850 nm to 950 nm. The reflectance from the terminal surfaceis comparable to that from the terminal surface, as the first and second layered filmsandwere constructed of materials having relatively low absorbance in the referenced wavelength range. As shown, throughout the wavelength range of 860 nm to 950 nm, the reflectance is less than 1.6%. Within the wavelength range of 850 nm to 950 nm, the reflectance has a minimum value of approximately of less than 1.0% (approximately 0.8%) at a wavelength of 925 nm.

10 FIG. 36 38 24 24 38 24 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 1 has a transmittance less than 12% throughout the visible spectrum for light incident on the windowat angles of incidence of less than or equal to 15°. From 400 nm to 650 nm, the transmittance in the visible spectrum is less than 3%. For wavelengths less than 600 nm, the transmittance in the visible spectrum is less than 0.2%. It is believed that these low transmission values are due in part to the absorbance of visible light by the silicon layers in the second layered film. The windowexhibits an average transmittance that is less than or equal to 5.0% over the wavelength range of 400 nm to 700 nm.

11 11 FIGS.A andB 11 FIG. 1 FIG. 36 38 24 44 44 24 26 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 1 has a dark appearance when viewed from the terminal surfaceof the first layered film.provides simulated CIELAB reflected color data for Example 1 for light reflected off of the terminal surface. The color of the reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown, the a* values ranges from about 0 to about 4.5, while the b* values ranges from about −0.8 to about 0.8. This indicates that the windowaccording to example 1 has a neutral appearance when viewed form the external environment(see).

11 FIG.B 1 FIG. 44 24 26 depicts modelled CIELAB lightness L* values of reflection as a function of angle of incidence on the terminal surface. As shown, for angles of incidence less than or equal to 60°, the lightness L* value is less than or equal to 35. For angles of incidence less than or equal to 50°, the lightness L* value is less than or equal to 25. For angles of incidence less than or equal to 35°, the lightness L* value is less than or equal to 20. This indicates that the windowaccording to example 1 has a dark appearance when viewed form the external environment(see).

12 FIG. 12 FIG. 12 FIG. 36 24 24 24 24 24 reveals nanoindentation hardness measured as a function of depth for a sample constructed in accordance with Example 1 herein. The hardness values were simulated as being subjected to the Berkovich Indenter Hardness Test described herein on the side of the first layered film. The sample was measured for a range of depths form 50 nm to 1000 nm. As depicted in, the sample exhibited a maximum hardness at approximately 750 nm in depth of greater than 15.5 GPa. Without wishing to be bound by theory, it is believed that the maximum hardness lies above the scratch resistant layers due to the stress fields caused by the indenter propagating beneath the scratch resistant layer once the depth reaches 1050 nm. As demonstrated by, the windowaccording to Example 1 exhibits a nanoindentation hardness of greater than 8 GPa throughout a depth range of 50 nm to 1000 nm. The windowaccording to Example 1 also exhibits a nanoindentation hardness of greater than 10 GPa throughout a depth range of 100 nm to 1000 nm. The windowaccording to Example 1 also exhibits a nanoindentation hardness of greater than 12 GPa throughout a depth range of 200 nm to 1000 nm. The windowaccording to Example 1 also exhibits a nanoindentation hardness of greater than 14 GPa throughout a depth range of 400 nm to 1000 nm. The windowaccording to Example 1 also exhibits a nanoindentation hardness of greater than 15 GPa throughout a depth range of 600 nm to 1000 nm. This indicates that this example provides favorable scratch/damage resistance for various applications.

Embodiments of the present disclosure can be further understood in view of the following information.

36 38 40 24 12 In embodiments, one of the first layered filmand the second layered filmcomprises one or more layers formed of a transparent conductive oxide (“TCO”) material. The TCO material can replace one of the layers of higher refractive index material. The layer(s) of TCO material can be communicatively (e.g., conductively) coupled to a power source (not depicted) for heating the window. This heating facilitates the one or more LiDAR systemsoperating in low temperature environments. The TCO material may be selected from suitable optically transparent and electrically conductive materials, such as indium tin oxide (“ITO”), aluminum-doped zinc oxide (“AZO”), and indium-doped cadmium oxide. In embodiments, ITO is preferred due to superior heat durability over certain other existing TCO materials.

38 48 38 30 24 42 30 30 36 38 38 40 30 40 30 In embodiments, the layer(s) of TCO material are disposed in the second layered film. In some embodiments, the layer(s) of TCO material are disposed more proximate to the terminal surfacethan absorber layers (e.g., Si layers) located in the second layered filmsuch that the absorber layers are disposed between the layer(s) of TCO material and the substrate. Such a construction beneficially facilitates the addition of the TCO material without effecting the dark, opaque appearance of the windowdescribed herein. In aspects, the layer(s) of TCO material are disposed between layers of lower refractive index materialsdue to the intermediate refractive index thereof. However, embodiments are contemplated in which the layer(s) of TCO material are disposed adjacent to the substrate(e.g., between the substrateand one of the first and second layered filmsand). In aspects, the second layered filmcomprises a single layer of TCO material (e.g., ITO), with the single layer of TCO material being the layer of the higher refractive index materialthat is furthest from the substrate, with a plurality of absorber (e.g. Si) layers (and/or other layers of the higher refractive index materials) being disposed between the layer of TCO material and the substrate.

24 24 24 The thickness of the layer(s) of TCO material can be selected based on a number of factors, including a desired a sheet resistance that is necessary to achieve heating of the windowand the desired optical performance of the window. In embodiments, each of the layers of TCO material has a thickness that is less than or equal to 50 nm (e.g., less than or equal to 45 nm, less than or equal to 40 nm, less than or equal to 35 nm, less than or equal to 30 nm, less than or equal to 25 nm, greater than or equal to 20 nm and less than or equal to 30 nm) and an optical extinction coefficient at 905 nm that is less than or equal to 0.05 (e.g., less than or equal to 0.04). Embodiments where the layer(s) of TCO material have thicknesses greater than 50 nm are also contemplated. When the extinction coefficient is less than 0.05 throughout a spectral range of 840 nm to 1020 nm, absorption over the wavelength range of interest is beneficially minimized to maintain the superior transmission performance of the layered films described herein. That is, the layer(s) of TCO material do not significantly effect the transmittance properties of the windowat the wavelength range of interest, while providing adequate sheet resistance to facilitate heating. It has been found that ITO is a suitable TCO material, able to provide suitable sheet resistance for heating when deposited at thicknesses from 20 nm to 30 nm, while having an optical extinction coefficient of less than 0.05 over the wavelength range of interest.

24 36 38 38 24 36 32 30 24 38 34 30 30 30 18 320 6 6 FIGS.A-B Example 2—the windowof Example 2 included a first layered filmand a second layered film. The second layered filmincluded layers of a silicon material described as the “Low k” material with respect toherein. The windowof Example 2 included a first layered filmover a first surfaceof a substrate. The windowalso included a second layered filmover a second surfaceof the substrate. In Example 2, the substratewas a laminate described in U.S. Provisional Patent Application No. 63/349,764, entitled “Laminate Windows for Infrared Sensing Systems,” filed on Jun. 7, 2022, and hereby incorporated by reference in its entirety. Particularly, the substrateincluded a first glass ply (as the outer ply away from the radiation emitter and sensor) that was a 2.85 mm thick layer of unstrengthened aluminosilicate glass, an interlayer of optically clear adhesive, and a second (inner) glass plythat was a 1 mm thick layer of chemically strengthened aluminosilicate glass.

36 42 40 40 44 32 36 2 The first layered filmincluded thirty-one (31) alternating layers of SiOas the lower refractive index materialand SiN as the higher refractive index material. Layer 22 was the scratch resistant layer of the higher refractive index material, having a thickness of 2038.98 nm. Layers 1-21 were optical control layers having a combined thickness of 1352 nm separating the scratch resistant layer from the terminal surface. Layers 23-31 were index matching layers separating the scratch resistance layer from the first surfaceand having a combined thickness of 380.87 nm. In this example, the scratch resistant layer constituted 54.06% of the thickness of the first layered film.

38 42 40 42 40 40 30 40 30 38 40 48 24 2 The second layered filmincluded twenty-three (23) alternating layers of the lower refractive index materialand the higher refractive index material. In this example, the lower refractive index materialwas SiO, while the higher refractive index materialwas a combination of SiN, Si, and ITO. As shown, layers 35, 37, 39, and 41—the four closest layers of the higher refractive index materialto the substrate—were SiN, while the remaining layers of the higher refractive index materialwere the Low k Si and ITO. Layer 43—the Si layer most proximate to the substrate—was the narrowest Si layer, with a thickness of 12.22 nm. The combined thickness of the silicon layers was 485.01 nm, which constituted 35.9% of the total thickness of the second layered film. Layer 55, was a layer of TCO material. As shown, the TCO layer had a refractive index of 1.72 at 905 nm, which is less than half of that of the closest layers of the higher refractive index material. The thickness of the TCO layer was 22 nm to provide a desired sheet resistance for heating purposes. The TCO was beneficially located rearward (closer to the terminal surface) than the silicon layers. As described herein, such placement of the TCO layer is beneficial because visible light is absorbed by the silicon layers and, as a result, does not reach the TCO layer. The addition of the TCO layer in this manner beneficially prevents the TCO layer from altering the appearance of the windowdescribed herein, while also adding functionality.

36 38 13 15 FIGS.- The thicknesses of the layers of the first layered filmand the second layered filmwere configured as set forth in Table 2 below and used to calculate the transmittance, reflectance. CIELAB color space and lightness values of reflection values set forth in.

TABLE 2 Example 2 Layer Design Refractive Physical Index Thickness Layer Material @905 nm (nm) Medium Air 1 Perfluoropolyether 1-4 4-8 1 SiO2 1.4603 115.98 2 SiN 2.0669 33.95 3 SiO2 1.4603 18.3 4 SiN 2.0669 97.81 5 SiO2 1.4603 23.04 6 SiN 2.0669 24.61 7 SiO2 1.4603 191.22 8 SiN 2.0669 17.29 9 SiO2 1.4603 25.43 10 SiN 2.0669 164.64 11 SiO2 1.4603 28.29 12 SiN 2.0669 25.33 13 SiO2 1.4603 235.11 14 SiN 2.0669 28.05 15 SiO2 1.4603 35.81 16 SiN 2.0669 37.94 17 SiO2 1.4603 17.32 18 SiN 2.0669 145.89 19 SiO2 1.4603 10.93 20 SiN 2.0669 58.18 21 SiO2 1.4603 16.88 22 SiN 2.0669 2038.98 23 SiO2 1.4603 16.63 24 SiN 2.0669 48.52 25 SiO2 1.4603 42.12 26 SiN 2.0669 33.29 27 SiO2 1.4603 65.34 28 SiN 2.0669 17.74 29 SiO2 1.4603 95.15 30 SiN 2.0669 11.52 31 SiO2 1.4603 50.56 Substrate Aluminosilicate glass (2320) 1.4985 2850000 Substrate Aluminosilicate glass (2320) 1.4985 1000000 34 SiO2 1.4603 64.68 35 SiN 2.0669 19.99 36 SiO2 1.4603 46.02 37 SiN 2.0669 45.11 38 SiO2 1.4603 14.57 39 SiN 2.0669 208.21 40 SiO2 1.4603 25.92 41 SiN 2.0669 58.7 42 SiO2 1.4603 15.47 43 Si 3.6748 12.22 44 SiO2 1.4603 20.58 45 Si 3.6748 30.03 46 SiO2 1.4603 13.17 47 Si 3.6748 99.03 48 SiO2 1.4603 15.76 49 Si 3.6748 145.62 50 SiO2 1.4603 11.33 51 Si 3.6748 174.37 52 SiO2 1.4603 69.29 53 Si 3.6748 23.74 54 SiO2 1.4603 186.27 55 ITO 1.7187 (550 22 nm) 56 SiO2 1.4603 27.12 Medium Air 1

13 FIG. 13 FIG. 13 FIG. 24 24 36 38 24 32 34 36 38 24 is a plot of a modelled transmittance of the windowaccording to Example 2 of light that is incident on the windowat a 15° angle of incidence and a 60° angle of incidence throughout the spectral range of 350 nm to 1500 nm. As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 2 has a percentage transmittance of above 95 percent for light incident on the first surfaceor the second surfaceat angles of incidence of less than 15° throughout a wavelength range extending from 850 nm to 950 nm. Indeed, throughout the wavelength range of 850 nm to 950 nm, the window exhibits a transmittance of greater than 96% for light at a 15° angle of incidence. Additionally, as shown in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 2 has a polarization-averaged transmittance, calculated a wavelength range of interest from 850 nm to 950 nm, of greater than 89% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

13 FIG. 13 FIG. 36 38 24 24 44 24 38 36 38 24 24 44 As is further revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 2 has a transmittance less than 10% throughout the visible spectrum for light incident on the window(the terminal surface) at angles of incidence of less than or equal to 15°. The windowaccording to Example 2 exhibits an average transmittance of less than 2% from 400 nm to 700 nm at normal incidence. These low transmission values are due in part to the absorbance of visible light by the silicon layers in the second layered film. As is further revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 2 has a transmittance less than 13% throughout the visible spectrum for light incident on the window(the terminal surface) at angles of incidence of less than or equal to 60°.

14 FIG. 36 38 24 44 36 30 44 48 36 38 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 2 has a polarization-averaged percentage reflectance off of the terminal surfaceof the first layered filmof under 1% for light incident on the substrateat an angle of incidence of 15° within the approximate wavelength range of 850 nm to 950 nm. The reflectance from the terminal surfaceis comparable to that from the terminal surface, as the first and second layered filmsandwere constructed of materials having relatively low absorbance in the referenced wavelength range.

15 FIG. 15 FIG. 1 FIG. 36 38 24 44 44 24 26 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 2 has a dark appearance when viewed from the terminal surfaceof the first layered film.provides simulated CIELAB reflected color data for Example 2 for light reflected off of the terminal surface. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown, the a* values ranges from about −1.2 to about 0.8, while the b* values ranges from about −0.3 to about 6. This indicates that the windowaccording to Example 2 has a neutral appearance when viewed form the external environment(see).

38 48 40 48 38 30 48 48 42 40 48 24 48 38 It has been found that, in the second layered film, separating the silicon layers from the terminal surfacewith one or more layers of another layer of the higher refractive index materialscan provide improve anti-reflective performance in the 50 nm wavelength range of interest, particularly from the terminal surface. Accordingly, in embodiments, an innermost silicon layer of the second layered filmthat is furthest from the substrate(most proximate the terminal surface) can be separated from the terminal surfaceby an “inner AR stack” comprising at least one layer of the lower refractive index materialsand at least one layer of the higher refractive index materialsthat are not silicon (e.g., SiN or other suitable higher refractive index material). When included, the inner AR stack may also be disposed between this innermost silicon layer and the terminal surface. While the design according to Example 2 herein exhibits favorable performance, it has been found that the addition of this inner AR stack lowers the reflectance of the windowwithin the 50 nm wavelength range of interest, particularly at lower angles of incidence on the terminal surfacethat are less than or equal to 15°. The inner AR stack can enable a maximum reflectance that is less than or equal to 0.5% throughout the wavelength range of 890 nm to 950 nm for light incident on the second layered filmat angles of incidence that are less than or equal to 15°.

38 40 42 40 48 24 In embodiments, the inner AR stack of the second layered filmcomprises at least 2 (e.g., at least 3, at least 4) layers of the higher refractive index materialsthat are not silicon or a TCO layer such that the inner AR stack comprises at least 4 (e.g., at least 6, at least 8) alternating layers of the lower refractive index materialsand the higher refractive index materials. Moreover, a TCO layer, such as that described herein with respect to Example 2, can be incorporated between the inner AR stack and the terminal surfaceto facilitate heating without disrupting the appearance of the window, as described herein with respect to Example 2.

24 36 38 38 24 36 32 30 24 38 34 30 30 30 18 320 6 6 FIGS.A-B Example 3—the windowof Example 3 included a first layered filmand a second layered film. The second layered filmincluded layers of a silicon material described as the “Low k” material with respect toherein. The windowof Example 3 included a first layered filmover a first surfaceof a substrate. The windowalso included a second layered filmover a second surfaceof the substrate. In Example 3, the substratewas a laminate described in U.S. Provisional Patent Application No. 63/349,764, entitled “Laminate Windows for Infrared Sensing Systems,” filed on Jun. 7, 2022, and hereby incorporated by reference in its entirety. Particularly, the substrateincluded a first glass ply (as the outer ply away from the radiation emitter and sensor) that was a 2.85 mm thick layer of unstrengthened aluminosilicate glass, an interlayer of optically clear adhesive, and a second (inner) glass plythat was a 1 mm thick layer of chemically strengthened aluminosilicate glass.

36 42 40 40 44 32 36 2 The first layered filmincluded thirty-one (31) alternating layers of SiOas the lower refractive index materialand SiN as the higher refractive index material. Layer 22 was the scratch resistant layer of the higher refractive index material, having a thickness of 2038.98 nm. Layers 1-21 were optical control layers having a combined thickness of 1226.23 nm separating the scratch resistant layer from the terminal surface. Layers 23-31 were index matching layers separating the scratch resistance layer from the first surfaceand having a combined thickness of 355.85 nm. In this example, the scratch resistant layer constituted 55.83% of the thickness of the first layered film.

38 42 40 42 40 40 30 30 38 48 24 2 The second layered filmincluded thirty-three (33) alternating layers of the lower refractive index materialand the higher refractive index material. In this example, the lower refractive index materialwas SiO, while the higher refractive index materialwas a combination of SiN, Si, and ITO. As shown, layers 35, 37, and 39—the three closest layers of the higher refractive index materialto the substrate—were SiN. Layers 41, 43, 45, 47, 49, 51, 53, 55, and 57 where silicon layers. Layer 41—the Si layer most proximate to the substrate—was the narrowest Si layer, with a thickness of 9.55 nm. The combined thickness of the silicon layers was 742.34 nm, which constituted 21.8% of the total thickness of the second layered film. Layer 65 was a layer of TCO material. As shown, the TCO layer had a refractive index of 1.54. The TCO was beneficially located rearward (closer to the terminal surface) than the silicon layers. As described herein, such placement of the TCO layer is beneficial because visible light is absorbed by the silicon layers and, as a result, does not reach the TCO layer. The addition of the TCO layer in this manner beneficially prevents the TCO layer from altering the appearance of the windowdescribed herein, while also adding functionality.

48 38 24 2 In Example 3, layers 58-64 separate the silicon layers from the TCO layer and represent an inner AR stack, with the inner AR stack including SiN as the higher refractive index material. As shown, three SiN layers separate the innermost silicon layer from the terminal surface. The inner AR stack included seven layers with a combined thickness of 1251.11 nm, representing 36.82% of the total thickness of the second layered film. As shown, the inner AR stack included the two relatively layers of SiO(lays 58 and 62) having thicknesses greater than 350 nm. Such thick layers aid in providing particularly low reflectance on the inner side of the window, preventing back reflections of emitted radiation from causing signal noise.

36 38 16 18 FIGS.- The thicknesses of the layers of the first layered filmand the second layered filmin Example 3 were configured as set forth in Table 3 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values set forth in.

TABLE 3 Example 3 Layer Design Refractive Physical Index Thickness Layer Material @905 nm (nm) Medium Air 1 Perfluoropolyether 1-4 4-8 1 SiO2 1.4603 115.98 2 SiN 2.0669 33.95 3 SiO2 1.4603 18.3 4 SiN 2.0669 97.81 5 SiO2 1.4603 23.04 6 SiN 2.0669 24.61 7 SiO2 1.4603 191.22 8 SiN 2.0669 17.29 9 SiO2 1.4603 25.43 10 SiN 2.0669 164.64 11 SiO2 1.4603 28.29 12 SiN 2.0669 25.33 13 SiO2 1.4603 235.11 14 SiN 2.0669 28.05 15 SiO2 1.4603 35.81 16 SiN 2.0669 37.94 17 SiO2 1.4603 17.32 18 SiN 2.0669 145.89 19 SiO2 1.4603 10.93 20 SiN 2.0669 58.18 21 SiO2 1.4603 16.88 22 SiN 2.0669 2038.98 23 SiO2 1.4603 16.63 24 SiN 2.0669 48.52 25 SiO2 1.4603 42.12 26 SiN 2.0669 33.29 27 SiO2 1.4603 65.34 28 SiN 2.0669 17.74 29 SiO2 1.4603 95.15 30 SiN 2.0669 11.52 31 SiO2 1.4603 50.56 Substrate Aluminosilicate glass (2320) 1.4985 2850000 Substrate Aluminosilicate glass (2320) 1.4985 1000000 34 SiO2 1.46757 25 35 SiN 2.01527 8.14 36 SiO2 1.46757 242.94 37 SiN 2.01527 14.89 38 SiO2 1.46757 63.26 39 SiN 2.01527 60.51 40 SiO2 1.46757 13.57 41 Si 3.67482 9.55 42 SiO2 1.46757 25.61 43 Si 3.67482 153.9 44 SiO2 1.46757 22.32 45 Si 3.67482 105.03 46 SiO2 1.46757 44.02 47 Si 3.67482 23.75 48 SiO2 1.46757 465.16 49 Si 3.67482 138.17 50 SiO2 1.46757 113.89 51 Si 3.67482 42.11 52 SiO2 1.46757 15.28 53 Si 3.67482 94.4 54 SiO2 1.46757 56.31 55 Si 3.67482 155.71 56 SiO2 1.46757 71.19 57 Si 3.67482 19.72 58 SiO2 1.46757 356.34 59 SiN 2.01527 264.55 60 SiO2 1.46757 44.11 61 SiN 2.01527 90.21 62 SiO2 1.46757 379.05 63 SiN 2.01527 99.45 64 SiO2 1.46757 17.4 65 ITO 1.54307 22 66 SiO2 1.46757 140.08 Medium Air 1

16 FIG. 16 FIG. 24 24 36 38 24 32 34 is a plot of a modelled transmittance (polarization-averaged) of the windowaccording to Example 3 for light that is incident on the windowat a 15° angle of incidence and a 60° angle of incidence throughout the spectral range of 350 nm to 1500 nm. As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 3 has a percentage transmittance of above 95 percent for light incident on the first surfaceor the second surfaceat angles of incidence of less than 15° throughout a wavelength range extending from 850 nm to 950 nm. Indeed, throughout the wavelength range of 850 nm to 950 nm, the window exhibits a transmittance of greater than 96% for light at a 15° angle of incidence.

16 FIG. 16 FIG. 36 38 24 36 38 24 24 44 24 Additionally, as shown in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 3 has a polarization-averaged transmittance, calculated over a wavelength range of interest from 850 nm to 950 nm, of greater than 85% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface. Further, as revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 3 has a transmittance less than 5% throughout the visible spectrum for light incident on the window(the terminal surface) at angles of incidence of less than or equal to 60°. The windowaccording to Example 3 exhibits an average transmittance of less than 0.1% from 400 nm to 700 nm at normal incidence. The reduced visible transmittance as compared to Example 3 is due to the larger number of silicon layers and the combined thickness of the silicon layers.

17 FIG.A 17 FIG.B 36 38 24 44 36 30 44 48 36 38 24 44 36 48 38 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 3 has a polarization-averaged percentage reflectance off of the terminal surfaceof the first layered filmof under 1% for light incident on the substrateat an angle of incidence of 15° within the approximate wavelength range of 850 nm to 950 nm on either of the terminal surfacesand. As is revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 3 has an average percentage reflectance off of both the terminal surfaceof the first layered filmand the terminal surfaceof the second layered filmof under 0.5% for light incident at an angle of incidence of 15° within the approximate wavelength range of 890 nm to 950 nm (polarizations averaged), which is also lower than that of Example 2 due to the addition of the inner AR stack.

18 FIG. 18 FIG. 1 FIG. 36 38 24 44 44 24 26 44 24 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 3 has a dark appearance when viewed from the terminal surfaceof the first layered film.provides simulated CIELAB reflected color data for Example 3 for light reflected off of the terminal surface. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown, the a* values ranges from about −2.3 to about 4.5, while the b* values ranges from about −1.65 to about 0. This indicates that the windowaccording to Example 3 has a neutral appearance when viewed form the external environment(see). The windows according to Examples 2 and 3 also exhibited an L* value of less than 26 for light incident on the terminal surfaceat an angle of incidence ranging from 0° to 45°, thereby facilitating a perceived darkness of the windowat those viewing angles.

38 44 48 40 44 44 Alternative embodiments can be formed by modifying Example 3 by increasing the number of silicon layers in the second layered filmand reducing the relative number of layers in the inner AR stack. These changes can beneficially flat out the reflectance spectra from the side of the terminal surfaceas compared with Example 3, while still exhibiting the low reflectance from light incident on the terminal surface. Particularly, it has been found that providing at least 10 (e.g., 10, 11, 12, 13, 14, or even 15) Si layers in the second layered film while reducing the size of the inner AR stack to include less than 3 (i.e., 1 or 2) of the layers of the higher refractive index materialsbetween the Si layers and the TCO layer beneficially leads to a flatter reflection spectrum around the 50 nm wavelength range of interest. Such a flatter reflection spectrum beneficially increases manufacturing tolerances and provides greater production throughput when achieving the high transmittance and low reflectance performance at the 50 nm wavelength range of interest described herein. Windows including this greater number of silicon layers and reduced inner AR stacks can achieve a reflectance range (max−min) of less than 0.05% for light over a wavelength range from 850 nm to 970 nm that is incident on the terminal surfaceat an angle of incidence of 15°. Such embodiments can also achieve a reflectance range (max−min) of less than 3% for light over a wavelength range from 850 nm to 950 nm that is incident on the terminal surfaceat an angle of incidence of 60°.

24 36 38 38 24 36 32 30 24 38 34 30 30 Example 4—the windowof Example 4 included a first layered filmand a second layered film. The second layered filmincluded layers of a silicon material described as the “Low k” material herein. The windowof Example 4 included a first layered filmover a first surfaceof a substrate. The windowalso included a second layered filmover a second surfaceof the substrate. In Example 4, the substratewas the same construction as the Example 3.

36 42 40 40 44 32 36 2 The first layered filmincluded twenty-seven (27) alternating layers of SiOas the lower refractive index materialand SiN as the higher refractive index material. Layer 20 was the scratch resistant layer of the higher refractive index material, having a thickness of 2055.93 nm. Layers 1-19 were optical control layers having a combined thickness of 1108.71 nm separating the scratch resistant layer from the terminal surface. Layers 21-27 were index matching layers separating the scratch resistance layer from the first surfaceand having a combined thickness of 222.41 nm. In this example, the scratch resistant layer constituted 60.7% of the thickness of the first layered film.

38 42 40 42 40 40 30 30 38 48 2 The second layered filmincluded thirty-three (33) alternating layers of the lower refractive index materialand the higher refractive index material. In this example, the lower refractive index materialwas SiO, while the higher refractive index materialwas a combination of SiN, Si, and ITO. As shown, layers 29 and 31—the two closest layers of the higher refractive index materialto the substrate—were SiN. Layers 33, 35, 37, 39, 41, 43, 45, 47, 49, 41, 43, and 55 where silicon layers. The Example 4 thus contains a greater number of silicon layers than the Example 3. Layer 33—the Si layer most proximate to the substrate—was the narrowest Si layer, with a thickness of 8.05 nm. The combined thickness of the silicon layers was 522.03 nm, which constituted 31.7% of the total thickness of the second layered film. As such, compared to the Example 3, the Example 4 contained a greater number of silicon layers. While the combined thickness of the silicon layers was less in Example 4 than in the Example 3, the combined thickness constituted a greater percentage of the overall thickness of the second layered film (more than 30%). Layer 59 was a layer of TCO material. As shown, the TCO layer had a refractive index of 1.54. The TCO was beneficially located rearward (closer to the terminal surface) than the silicon layers.

48 38 38 48 2 In Example 4, layers 56-58 separate the silicon layers from the TCO layer and represent an inner AR stack, with the inner AR stack including SiN as the higher refractive index material. As shown, one SiN layer separates the innermost silicon layer from the terminal surface. The inner AR stack included three layers with a combined thickness of 109.28 nm, representing 6.62% of the total thickness of the second layered film. Thus, the inner AR stack was much smaller in the Example 4 as compared to the Example 3, and made up much less of a portion of the entire thickness (less than 10%) of the second layered film. Moreover, the inner AR stack in the Example 4 included two relatively thin SiOlayers (layers 56 and 58), with thicknesses of 10 nm and 20 nm, respectively. Without wishing to be bound by theory, the thinner inner AR stack in Example 4 were compensated through the additional Si layers, which facilitated achieving favorable reflectance performance for light off the terminal surface.

36 38 19 21 FIGS.- The thicknesses of the layers of the first layered filmand the second layered filmin Example 4 were configured as set forth in Table 4 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values set forth in.

TABLE 4 Example 4 Layer Design Refractive Physical Index Thickness Layer Material @905 nm (nm) Medium Air 1 Perfluoropolyether 1-4 4-8 1 SiO2 1.46757 123.09 2 SiN 2.01527 21.51 3 SiO2 1.46757 16.32 4 SiN 2.01527 104.99 5 SiO2 1.46757 27.08 6 SiN 2.01527 15.97 7 SiO2 1.46757 174.33 8 SiN 2.01527 13.57 9 SiO2 1.46757 36.02 10 SiN 2.01527 29.66 11 SiO2 1.46757 12.41 12 SiN 2.01527 126.56 13 SiO2 1.46757 28.18 14 SiN 2.01527 23.88 15 SiO2 1.46757 232.35 16 SiN 2.01527 18.99 17 SiO2 1.46757 46.96 18 SiN 2.01527 40.33 19 SiO2 1.46757 16.51 20 SiN 2.01527 2055.93 21 SiO2 1.46757 14.01 22 SiN 2.01527 45.65 23 SiO2 1.46757 36.81 24 SiN 2.01527 28.78 25 SiO2 1.46757 59.65 26 SiN 2.01527 12.51 27 SiO2 1.46757 25 Substrate Aluminosilicate glass (2320) 1.4985 2850000 Substrate Aluminosilicate glass (2320) 1.4985 1000000 28 SiO2 1.46757 25 29 SiN 2.01527 13.59 30 SiO2 1.46757 64 31 SiN 2.01527 29.18 32 SiO2 1.46757 36.42 33 Si 3.67482 8.05 34 SiO2 1.46757 44.05 35 Si 3.67482 21.35 36 SiO2 1.46757 29.05 37 Si 3.67482 43.66 38 SiO2 1.46757 18.88 39 Si 3.67482 45.69 40 SiO2 1.46757 18.25 41 Si 3.67482 125.32 42 SiO2 1.46757 35.34 43 Si 3.67482 28.38 44 SiO2 1.46757 49.14 45 Si 3.67482 130.47 46 SiO2 1.46757 62.61 47 Si 3.67482 22.6 48 SiO2 1.46757 80.51 49 Si 3.67482 41.62 50 SiO2 1.46757 59.92 51 Si 3.67482 31.43 52 SiO2 1.46757 165.16 53 Si 3.67482 10.83 54 SiO2 1.46757 139.6 55 Si 3.67482 12.63 56 SiO2 1.46757 10 57 SiN 2.01527 79.28 58 SiO2 1.46757 20 59 ITO 1.54307 22 60 SiO2 1.46757 124.32 Medium Air 1

19 FIG. 19 FIG. 24 24 36 38 24 32 34 is a plot of a modelled transmittance (polarization-averaged) of the windowaccording to Example 4 for light that is incident on the windowat a 15° angle of incidence and a 60° angle of incidence throughout the spectral range of 350 nm to 1600 nm. As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 4 has a percentage transmittance of above 95 percent for light incident on the first surfaceor the second surfaceat angles of incidence of less than 15° throughout a wavelength range extending from 850 nm to 950 nm. Indeed, throughout the wavelength range of 850 nm to 950 nm, the window exhibits a transmittance of greater than 95% for light at a 15° angle of incidence.

19 FIG. 19 FIG. 36 38 24 36 38 24 24 44 44 24 24 Additionally, as shown in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 4 has a polarization-averaged transmittance, calculated over a wavelength range of interest from 850 nm to 950 nm, of greater than 90% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface. Further, as revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 4 has a transmittance less than 20% throughout the visible spectrum for light incident on the window(the terminal surface) at angles of incidence of less than or equal to 60°. At 60° angle of incidence on the terminal surface, the windowaccording to Example 4 exhibits a transmittance that is less than 0.1% throughout the wavelength range from 400 nm to 600 nm. The windowaccording to Example 4 exhibits an average transmittance of less than 1% from 400 nm to 700 nm at both normal and a 15° angle of incidence.

20 FIG.A 20 FIG.B 36 38 24 44 36 30 36 38 24 48 38 24 44 48 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 4 has a polarization-averaged percentage reflectance off of the terminal surfaceof the first layered filmof under 1% for light incident on the substrateat an angle of incidence of 15° within the approximate wavelength range of 850 nm to 950 nm. As is revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 4 has an average percentage reflectance off of the terminal surfaceof the second layered filmof under 0.5% for light incident at an angle of incidence of 15° within the approximate wavelength range of 850 nm to 950 nm (polarizations averaged). The windowof Example 4 exhibits a polarization averaged reflectance of less than 10% for light within the approximate wavelength range of 850 nm to 950 nm and incident on either of the terminal surfacesandat a 60° angle of incidence.

20 20 20 FIGS.C,D, andE 20 20 FIGS.C andD 20 FIG.C 20 FIG.D 20 FIG.E 44 38 38 38 48 compare the reflectance performances over the wavelength range of 850 nm to 950 nm of the windows according to Example 3 and Example 4.are plots of polarization averaged reflectance for light incident on the terminal surfacesof Examples 3 and 4 at 15° and 60° angles of incidence, respectively. As is revealed in, the reconfiguration of the second layered filmin Example 4 provided lower reflectance (of under 0.1%) at a 15° angle of incidence throughout the wavelength range from 860 nm to 950 nm. The reflectance range (max-min) was also less than 0.05% for Example 4 for the 850 nm to 950 nm wavelength range, whereas Example 3 exhibited a range of almost 0.2%. As is revealed in, the reconfiguration of the second layered filmin Example 4 provided lower reflectance (of under 7%) at a 60° angle of incidence throughout the wavelength range from 850 nm to 950 nm. The reflectance range (max-min) was also less than 3% for Example 4 for the 850 nm to 950 nm wavelength range, whereas Example 3 exhibited a range of more than 5%. As is revealed in, the reconfiguration of the second layered filmin Example 4 provided lower reflectance (of under 0.2%) for light incident on the terminal surfaceat a 15° angle of incidence throughout the wavelength range from 850 nm to 950 nm. These results demonstrate both reduced reflectance and a flatter reflectance spectra throughout the 850 nm to 950 nm wavelength range of Example 4 as compared to Example 3. As described herein, render the layered films more easier to manufacture.

21 FIG. 21 FIG. 1 FIG. 36 38 24 44 44 24 26 44 24 As revealed in, the quantity, thicknesses, number, and materials of the first layered filmand the second layered filmhave been configured so that the windowof Example 4 has a dark appearance when viewed from the terminal surfaceof the first layered film.provides simulated CIELAB reflected color data for Example E for light reflected off of the terminal surface. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown, the a* values ranges from about −0.58 to about 0.9, while the b* values ranges from about −0.2 to about 1.4. This indicates that the windowaccording to Example 4 has a neutral appearance when viewed form the external environment(see). The windows according to Examples 2 and 3 also exhibited an L* value of less than 37 for light incident on the terminal surfaceat an angle of incidence ranging from 0° to 60°, thereby facilitating a perceived darkness of the windowat those viewing angles.

It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.